Test suite: use the qemu-xhci USB controller

https://www.kraxel.org/blog/2018/08/qemu-usb-tips/ reads "Unless you are running
an operating system museum just use -device qemu-xhci".

features/domains/default.xml

@@ -18,7 +18,7 @@
   <on_crash>restart</on_crash>
   <devices>
     <emulator>/usr/bin/qemu-system-x86_64</emulator>
-    <controller type='usb' index='0' model='nec-xhci'/>
+    <controller type='usb' index='0' model='qemu-xhci'/>
     <controller type='sata' index='0'/>
     <controller type='virtio-serial' index='0'/>
     <interface type='network'>