tests: fix missing test data for network port XML

The network port XML files were not including any usage of vlan
tags or port options, and one of the files was not even processed.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

tests/virnetworkportxml2xmldata/plug-network.xml

@@ -10,6 +10,11 @@
     <inbound average='1000' peak='4000' floor='2000' burst='1024'/>
     <outbound average='128' peak='256' burst='32768'/>
   </bandwidth>
+  <vlan trunk='yes'>
+    <tag id='2'/>
+    <tag id='1729'/>
+  </vlan>
+  <port isolated='yes'/>
   <rxfilters trustGuest='yes'/>
   <plug type='network' bridge='virbr0'/>
 </networkport>

tests/virnetworkportxml2xmltest.c

@@ -94,6 +94,7 @@ mymain(void)
     DO_TEST("plug-bridge-mactbl");
     DO_TEST("plug-direct");
     DO_TEST("plug-hostdev-pci");
+    DO_TEST("plug-network");
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }