Description of problem:
The guest with intel-iommu device enabled can not restore after managedsave.

Version-Release number of selected component (if applicable):
libvirt-3.2.0-9.virtcov.el7.x86_64
qemu-kvm-rhev-2.9.0-8.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1.Prepare a guest with q35 machine type and enable the intel-iommu device:
...
<os>
    <type arch='x86_64' machine='pc-q35-rhel7.4.0'>hvm</type>  -
    <boot dev='hd'/>
</os>
...
<iommu model='intel'/>
</devices>
...

2.start the guest:
#virsh start vm1-q35

3.Enable iommu in the guest:
(1)Edit file  "/etc/default/grub":
Append "intel_iommu=on" or "amd_iommu=on" to the value of "GRUB_CMDLINE_LINUX=......". Such as the following one:
GRUB_CMDLINE_LINUX="rd.md=0 rd.lvm=0 rd.dm=0 vconsole.keymap=us $([ -x /usr/sbin/rhcrashkernel-param ] && /usr/sbin/rhcrashkernel-param || :) rd.luks=0 vconsole.font=latarcyrheb-sun16 rhgb quiet intel_iommu=on"

(2)Then run the following command to generate the updated grub file:
# grub2-mkconfig -o /boot/grub2/grub.cfg
Reboot the guest.

4.Do managedsave:
#virsh managedsave vm1-q35
Domain vm1-q35 state saved by libvirt

5.Start the guest:
#virsh start vm1-q35
# virsh start vm1-q35
error: Failed to start domain vm1-q35
error: operation failed: job: unexpectedly failed

Actual results:
The guest with intel-iommu device enabled can not restore after managedsave. 

Expected results:
If the guest with intel-iommu device enabled can not restored after managedsave, libvirt should reject to do managedsave with the guest.

Additional info:
Could see the info below in the libvirtd.log:
Jun  8 09:58:43 localhost libvirtd: 22164: error : qemuMigrationCheckJobStatus:1425 : operation failed: job: unexpectedly failed
Jun  8 09:58:43 localhost systemd-machined: Machine qemu-2-vm1-q35 terminated.
Jun  8 09:58:43 localhost libvirtd: 22164: warning : qemuDomainObjStart:7112 : Unable to restore from managed state /var/lib/libvirt/qemu/save/vm1-q35.save. Maybe the file is corrupted