tests: changing network interface types when backend tag is defined.

Some test cases have the backend tag inside wrong interfaces. The backend xml
tag does not support <interface type='user|direct|hostdev'>. So this commit
changes some network types inside the interfaces that have backend defined.
Signed-off-by: NJulio Faracco <jcfaracco@gmail.com>

tests/qemuxml2argvdata/qemuxml2argv-tap-vhost-incorrect.xml

@@ -22,14 +22,16 @@
     </controller>
     <controller type='ide' index='0'/>
     <controller type='pci' index='0' model='pci-root'/>
-    <interface type='user'>
+    <interface type='network'>
       <mac address='52:54:00:e5:48:58'/>
+      <source network='default'/>
       <model type='e1000'/>
       <driver name='vhost' queues='5'/>
       <backend tap='/dev/null' vhost='/dev/zero'/>
     </interface>
-    <interface type='user'>
+    <interface type='network'>
       <mac address='52:54:00:e5:48:59'/>
+      <source network='default'/>
       <model type='virtio'/>
       <driver name='vhost' queues='1'/>
       <backend tap='/dev/null' vhost='/dev/zero'/>

tests/qemuxml2argvdata/qemuxml2argv-tap-vhost.xml

@@ -35,8 +35,9 @@
     </controller>
     <controller type='ide' index='0'/>
     <controller type='pci' index='0' model='pci-root'/>
-    <interface type='user'>
+    <interface type='network'>
       <mac address='52:54:00:e5:48:58'/>
+      <source network='default'/>
       <model type='virtio'/>
       <driver name='vhost' queues='5'/>
       <backend tap='/dev/null' vhost='/dev/zero'/>

tests/qemuxml2xmloutdata/qemuxml2xmlout-tap-vhost-incorrect.xml

@@ -26,14 +26,16 @@
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
     </controller>
     <controller type='pci' index='0' model='pci-root'/>
-    <interface type='user'>
+    <interface type='network'>
       <mac address='52:54:00:e5:48:58'/>
+      <source network='default'/>
       <model type='e1000'/>
       <backend tap='/dev/null'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
     </interface>
-    <interface type='user'>
+    <interface type='network'>
       <mac address='52:54:00:e5:48:59'/>
+      <source network='default'/>
       <model type='virtio'/>
       <driver name='vhost'/>
       <backend tap='/dev/null' vhost='/dev/zero'/>

tests/qemuxml2xmloutdata/qemuxml2xmlout-tap-vhost.xml

@@ -39,8 +39,9 @@
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
     </controller>
     <controller type='pci' index='0' model='pci-root'/>
-    <interface type='user'>
+    <interface type='network'>
       <mac address='52:54:00:e5:48:58'/>
+      <source network='default'/>
       <model type='virtio'/>
       <driver name='vhost' queues='5'/>
       <backend tap='/dev/null' vhost='/dev/zero'/>