Ensure Macvtap NICs can use a model

Defaults to virtio like a bridged NIC. Otherwise performance is abysmal.

client-cli/cli_lib/vm.py

@@ -574,9 +574,10 @@ def vm_networks_add(config, vm, network, macaddr, model, sriov, sriov_mode, rest
             )
         # Add a macvtap SR-IOV network
         elif sriov_mode == 'macvtap':
-            device_string = '<interface type="direct"><mac address="{macaddr}"/><source dev="{network}" mode="passthrough"/></interface>'.format(
+            device_string = '<interface type="direct"><mac address="{macaddr}"/><source dev="{network}" mode="passthrough"/><model type="{model}"/></interface>'.format(
                 macaddr=macaddr,
-                network=network
+                network=network,
+                model=model
             )
         else:
             return False, "ERROR: Invalid SR-IOV mode specified."

client-cli/pvc.py

@@ -1317,7 +1317,7 @@ def vm_network_get(domain, raw):
 )
 @click.option(
     '-m', '--model', 'model', default='virtio',
-    help='The model for the interface; must be a valid libvirt model. Not used for SR-IOV NETs.'
+    help='The model for the interface; must be a valid libvirt model. Not used for "netdev" SR-IOV NETs.'
 )
 @click.option(
     '-s', '--sriov', 'sriov', is_flag=True, default=False,