Description of problem:
hyperv features are not enabled when installing win7 by q35+uefi

Version-Release number of selected component (if applicable):
virt-manager-1.4.0-2.el7.noarch

How reproducible:
100%

Steps to Reproduce:
1. Open virt-manager
2. Install a windows 7 guest by ISO.
3. At step 5 of 5, choose "Customize configuration before install".
4. In Overview, set Firmware to UEFI and Chipset to Q35.
5. Update disk bus bype of IDE disk 1 and IDE CDROM 1 to sata (Q35 doesn't support IDE).
6. Click "Begin Installation".
7. Run "ps aux | grep $guest | grep hv" to check hv_* features.

Actual results:
No hyperv features are enabled.

# ps aux | grep win7-2 
qemu     28042 13.0 52.5 5273684 4150472 ?     Sl   16:33   0:27 /usr/libexec/qemu-kvm -name guest=win7-2,debug-threads=on -S -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-68-win7-2/master-key.aes -machine pc-q35-rhel7.3.0,accel=kvm,usb=off,vmport=off -cpu SandyBridge -drive file=/usr/share/OVMF/OVMF_CODE.secboot.fd,if=pflash,format=raw,unit=0,readonly=on -drive file=/var/lib/libvirt/qemu/nvram/win7-2_VARS.fd,if=pflash,format=raw,unit=1 -m 4096 -realtime mlock=off -smp 2,sockets=2,cores=1,threads=1 -uuid b3f1c0d6-d352-48ca-831a-1a247bbe74a9 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-68-win7-2/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime,driftfix=slew -global kvm-pit.lost_tick_policy=discard -no-hpet -no-reboot -global ICH9-LPC.disable_s3=1 -global ICH9-LPC.disable_s4=1 -boot strict=on -device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x1e -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x0 -device ich9-usb-ehci1,id=usb,bus=pcie.0,addr=0x1d.0x7 -device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pcie.0,multifunction=on,addr=0x1d -device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pcie.0,addr=0x1d.0x1 -device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pcie.0,addr=0x1d.0x2 -device virtio-serial-pci,id=virtio-serial0,bus=pci.2,addr=0x3 -drive file=/var/lib/libvirt/images/en_windows_7_ultimate_with_sp1_x64_dvd_u_677332.iso,format=raw,if=none,media=cdrom,id=drive-sata0-0-0,readonly=on -device ide-cd,bus=ide.0,drive=drive-sata0-0-0,id=sata0-0-0,bootindex=1 -drive file=/var/lib/libvirt/images/win7-2.qcow2,format=qcow2,if=none,id=drive-sata0-0-1 -device ide-hd,bus=ide.1,drive=drive-sata0-0-1,id=sata0-0-1,bootindex=2 -netdev tap,fd=26,id=hostnet0 -device rtl8139,netdev=hostnet0,id=net0,mac=52:54:00:6d:0c:e7,bus=pci.2,addr=0x1 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev spicevmc,id=charchannel0,name=vdagent -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.spice.0 -device usb-tablet,id=input0,bus=usb.0,port=1 -spice port=5900,addr=127.0.0.1,disable-ticketing,image-compression=off,seamless-migration=on -device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vram64_size_mb=0,vgamem_mb=16,bus=pcie.0,addr=0x1 -device intel-hda,id=sound0,bus=pci.2,addr=0x2 -device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -chardev spicevmc,id=charredir0,name=usbredir -device usb-redir,chardev=charredir0,id=redir0,bus=usb.0,port=2 -chardev spicevmc,id=charredir1,name=usbredir -device usb-redir,chardev=charredir1,id=redir1,bus=usb.0,port=3 -device virtio-balloon-pci,id=balloon0,bus=pci.2,addr=0x4 -msg timestamp=on

Expected results:
Hyperv features should be enabled for windows guest.

Additional info:
This only happends with win7+q35+uefi.