Description of problem:

If a VM is created from a Q35 Template but is set to i440FX at the time of 'New VM', the vm_devices are left behind with several PCI elements and addresses that are not compatible.
And the VM fails to start because it's XML is inconsistent:

2020-04-30 15:50:25,055+1000 ERROR (vm/49395e3c) [virt.vm] (vmId='49395e3c-1dd1-4144-9d48-87fbe64662f1') The vm start process failed (vm:934)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 868, in _startUnderlyingVm
    self._run()
  File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 2892, in _run
    dom = self._connection.defineXML(self._domain.xml)
  File "/usr/lib/python2.7/site-packages/vdsm/common/libvirtconnection.py", line 131, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vdsm/common/function.py", line 94, in wrapper
    return func(inst, *args, **kwargs)
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 3733, in defineXML
    if ret is None:raise libvirtError('virDomainDefineXML() failed', conn=self)
libvirtError: XML error: The device at PCI address 0000:00:02.0 cannot be plugged into the PCI controller with index='0'. It requires a controller that accepts a pcie-root-port.

The full XML generated by the engine is in the "Additional Info" section.

NOTE: This does not seem to happen if a VM is switched from Q35 to i440FX after creation, the change needs to be during the 'New VM' when creating from Template.
From a quick research, I think it could be because engine is not clearing the devices if the BIOS change is done during VM creaion, like it does on UpdateVm:
https://github.com/oVirt/ovirt-engine/blob/master/backend/manager/modules/bll/src/main/java/org/ovirt/engine/core/bll/UpdateVmCommand.java#L522

Version-Release number of selected component (if applicable):
rhvm-4.3.9.4-11.el7.noarch
vdsm-4.30.44-1.el7ev.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Create a dummy VM with Q35 chipset (no OS install needed)
2. Create Template from VM
3. Create VM2 from Template, while setting BIOS Type to i440FX Seabios (Default) in the New VM dialog.
4. Run VM2

Actual results:
VM fails to start

Expected results:
VM starts with proper i440FX definitions and devices

Additional info:

2020-04-30 15:50:24,908+10 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.CreateBrokerVDSCommand] (EE-ManagedThreadFactory-engine-Thread-95) [18b31f59-ba59-44d1-a122-894e7dbe30a6] VM <?xml version="1.0" encoding="UTF-8"?><domain type="kvm" xmlns:ovirt-tune="http://ovirt.org/vm/tune/1.0" xmlns:ovirt-vm="http://ovirt.org/vm/1.0">
  <name>TEST_VM</name>
  <uuid>49395e3c-1dd1-4144-9d48-87fbe64662f1</uuid>
  <memory>1048576</memory>
  <currentMemory>1048576</currentMemory>
  <iothreads>1</iothreads>
  <maxMemory slots="16">4194304</maxMemory>
  <vcpu current="1">16</vcpu>
  <sysinfo type="smbios">
    <system>
      <entry name="manufacturer">Red Hat</entry>
      <entry name="product">OS-NAME:</entry>
      <entry name="version">OS-VERSION:</entry>
      <entry name="serial">HOST-SERIAL:</entry>
      <entry name="uuid">49395e3c-1dd1-4144-9d48-87fbe64662f1</entry>
    </system>
  </sysinfo>
  <clock offset="variable" adjustment="0">
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="pit" tickpolicy="delay"/>
    <timer name="hpet" present="no"/>
  </clock>
  <features>
    <acpi/>
  </features>
  <cpu match="exact">
    <model>Skylake-Client</model>
    <feature name="spec-ctrl" policy="require"/>
    <feature name="ssbd" policy="require"/>
    <feature name="md-clear" policy="require"/>
    <topology cores="1" threads="1" sockets="16"/>
    <numa>
      <cell id="0" cpus="0" memory="1048576"/>
    </numa>
  </cpu>
  <cputune/>
  <devices>
    <input type="tablet" bus="usb"/>
    <channel type="unix">
      <target type="virtio" name="ovirt-guest-agent.0"/>
      <source mode="bind" path="/var/lib/libvirt/qemu/channels/49395e3c-1dd1-4144-9d48-87fbe64662f1.ovirt-guest-agent.0"/>
    </channel>
    <channel type="unix">
      <target type="virtio" name="org.qemu.guest_agent.0"/>
      <source mode="bind" path="/var/lib/libvirt/qemu/channels/49395e3c-1dd1-4144-9d48-87fbe64662f1.org.qemu.guest_agent.0"/>
    </channel>
    <controller type="virtio-serial" index="0" ports="16">
      <alias name="ua-034639a5-b812-43c1-a3d5-732ec631b8ee"/>
      <address bus="0x03" domain="0x0000" function="0x0" slot="0x00" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="8">
      <address bus="0x00" domain="0x0000" function="0x7" slot="0x02" type="pci"/>
    </controller>
    <video>
      <model type="qxl" vram="8192" heads="1" ram="65536" vgamem="16384"/>
      <alias name="ua-082d5003-30d6-4abf-b009-7d57298d1ddf"/>
    </video>
    <controller type="pci" model="pcie-root-port" index="16">
      <address bus="0x00" domain="0x0000" function="0x7" slot="0x03" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="14">
      <address bus="0x00" domain="0x0000" function="0x5" slot="0x03" type="pci"/>
    </controller>
    <graphics type="vnc" port="-1" autoport="yes" passwd="*****" passwdValidTo="1970-01-01T00:00:01" keymap="en-us">
      <listen type="network" network="vdsm-ovirtmgmt"/>
    </graphics>
    <rng model="virtio">
      <backend model="random">/dev/urandom</backend>
      <alias name="ua-1c052397-a709-4362-a4c0-e085b23631e8"/>
    </rng>
    <controller type="pci" model="pcie-root-port" index="2">
      <address bus="0x00" domain="0x0000" function="0x1" slot="0x02" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="3">
      <address bus="0x00" domain="0x0000" function="0x2" slot="0x02" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="12">
      <address bus="0x00" domain="0x0000" function="0x3" slot="0x03" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="15">
      <address bus="0x00" domain="0x0000" function="0x6" slot="0x03" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="13">
      <address bus="0x00" domain="0x0000" function="0x4" slot="0x03" type="pci"/>
    </controller>
    <graphics type="spice" port="-1" autoport="yes" passwd="*****" passwdValidTo="1970-01-01T00:00:01" tlsPort="-1">
      <channel name="main" mode="secure"/>
      <channel name="inputs" mode="secure"/>
      <channel name="cursor" mode="secure"/>
      <channel name="playback" mode="secure"/>
      <channel name="record" mode="secure"/>
      <channel name="display" mode="secure"/>
      <channel name="smartcard" mode="secure"/>
      <channel name="usbredir" mode="secure"/>
      <listen type="network" network="vdsm-ovirtmgmt"/>
    </graphics>
    <controller type="pci" model="pcie-root-port" index="5">
      <address bus="0x00" domain="0x0000" function="0x4" slot="0x02" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="7">
      <address bus="0x00" domain="0x0000" function="0x6" slot="0x02" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="6">
      <address bus="0x00" domain="0x0000" function="0x5" slot="0x02" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="9">
      <address bus="0x00" domain="0x0000" function="0x0" slot="0x03" type="pci" multifunction="on"/>
    </controller>
    <memballoon model="virtio">
      <stats period="5"/>
      <alias name="ua-9f8436d3-7291-4fbf-b5e0-3f85a8487e36"/>
      <address bus="0x04" domain="0x0000" function="0x0" slot="0x00" type="pci"/>
    </memballoon>
    <controller type="scsi" model="virtio-scsi" index="0">
      <driver iothread="1"/>
      <alias name="ua-ac24a3c9-6ce0-49e0-b811-4583ec285619"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="1">
      <address bus="0x00" domain="0x0000" function="0x0" slot="0x02" type="pci" multifunction="on"/>
    </controller>
    <controller type="sata">
      <address bus="0x00" domain="0x0000" function="0x2" slot="0x1f" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="11">
      <address bus="0x00" domain="0x0000" function="0x2" slot="0x03" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="4">
      <address bus="0x00" domain="0x0000" function="0x3" slot="0x02" type="pci"/>
    </controller>
    <controller type="pci" model="pcie-root-port" index="10">
      <address bus="0x00" domain="0x0000" function="0x1" slot="0x03" type="pci"/>
    </controller>
    <controller type="usb" model="piix3-uhci" index="0"/>
    <channel type="spicevmc">
      <target type="virtio" name="com.redhat.spice.0"/>
    </channel>
    <disk type="file" device="cdrom" snapshot="no">
      <driver name="qemu" type="raw" error_policy="report"/>
      <source file="" startupPolicy="optional">
        <seclabel model="dac" type="none" relabel="no"/>
      </source>
      <target dev="hdc" bus="ide"/>
      <readonly/>
      <alias name="ua-ba85d4d1-8143-469f-bb98-61dc020f7c25"/>
      <address bus="0" controller="0" unit="2" type="drive" target="0"/>
    </disk>
    <disk snapshot="no" type="file" device="disk">
      <target dev="sda" bus="scsi"/>
      <source file="/rhev/data-center/61facf2e-82aa-11ea-964e-52540019c104/0c384a7c-ae10-470e-82ae-a1f10728c156/images/5e398581-aa2c-4919-ac9b-bfd14aee5441/3f555307-e7bd-47f3-b9ca-ee1bbdfe88c6">
        <seclabel model="dac" type="none" relabel="no"/>
      </source>
      <driver name="qemu" io="threads" type="qcow2" error_policy="stop" cache="none"/>
      <alias name="ua-5e398581-aa2c-4919-ac9b-bfd14aee5441"/>
      <address bus="0" controller="0" unit="0" type="drive" target="0"/>
      <boot order="1"/>
      <serial>5e398581-aa2c-4919-ac9b-bfd14aee5441</serial>
    </disk>
  </devices>
  <pm>
    <suspend-to-disk enabled="no"/>
    <suspend-to-mem enabled="no"/>
  </pm>
  <os>
    <type arch="x86_64" machine="pc-i440fx-rhel7.6.0">hvm</type>
    <smbios mode="sysinfo"/>
  </os>
  <metadata>
    <ovirt-tune:qos/>
    <ovirt-vm:vm>
      <ovirt-vm:minGuaranteedMemoryMb type="int">1024</ovirt-vm:minGuaranteedMemoryMb>
      <ovirt-vm:clusterVersion>4.3</ovirt-vm:clusterVersion>
      <ovirt-vm:custom/>
      <ovirt-vm:device devtype="disk" name="sda">
        <ovirt-vm:poolID>61facf2e-82aa-11ea-964e-52540019c104</ovirt-vm:poolID>
        <ovirt-vm:volumeID>3f555307-e7bd-47f3-b9ca-ee1bbdfe88c6</ovirt-vm:volumeID>
        <ovirt-vm:imageID>5e398581-aa2c-4919-ac9b-bfd14aee5441</ovirt-vm:imageID>
        <ovirt-vm:domainID>0c384a7c-ae10-470e-82ae-a1f10728c156</ovirt-vm:domainID>
      </ovirt-vm:device>
      <ovirt-vm:launchPaused>false</ovirt-vm:launchPaused>
      <ovirt-vm:resumeBehavior>auto_resume</ovirt-vm:resumeBehavior>
    </ovirt-vm:vm>
  </metadata>
</domain>