network: use 'bridge' as actual type instead of 'network'

Ports allocated on virtual networks with type=nat|route|open all get
given an actual type of 'network'.

Only ports in networks with type=bridge use an actual type of 'bridge'.

This distinction makes little sense since the virtualization drivers
will treat both actual types in exactly the same way, as they're all
just bridge devices a VM needs to be connected to.

This doesn't affect user visible XML since the "actual" device XML
is internal only, but we need code to convert the data upgrades.

Reviewed-by: Laine Stump <laine@laine.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

tests/qemustatusxml2xmldata/migration-out-params-in.xml

@@ -343,7 +343,7 @@
       <interface type='network'>
         <mac address='52:54:00:59:59:91'/>
         <source network='default'/>
-        <actual type='network'>
+        <actual type='bridge'>
           <source bridge='virbr0'/>
         </actual>
         <target dev='vnet0'/>