qemu: Only setup vhost if virtType == "kvm"

vhost only works in KVM mode at the moment, and is infact compiled
out if the emulator is built for non-native architecture. While it
may work at some point in the future for plain qemu, for now it's
just noise on the command line (and which contributes to arm cli
breakage).

src/qemu/qemu_command.c

@@ -441,8 +441,10 @@ qemuOpenVhostNet(virDomainDefPtr def,
 {
     size_t i;
 
-    /* If the config says explicitly to not use vhost, return now */
-    if (net->driver.virtio.name == VIR_DOMAIN_NET_BACKEND_TYPE_QEMU) {
+    /* If running a plain QEMU guest, or
+     * if the config says explicitly to not use vhost, return now*/
+    if (def->virtType != VIR_DOMAIN_VIRT_KVM ||
+        net->driver.virtio.name == VIR_DOMAIN_NET_BACKEND_TYPE_QEMU) {
         *vhostfdSize = 0;
         return 0;
     }