virsh: tweak domif-getlink link state reporting message

According to docs, we only support 2 link states for an interface
up/down, 'up' being the default state if link state is unspecified in
domain's XML, so the message when no link state is provided should be
changed a little.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1141119

tools/virsh-domain-monitor.c

@@ -772,7 +772,7 @@ cmdDomIfGetLink(vshControl *ctl, const vshCmd *cmd)
     if ((state = virXPathString("string(./link/@state)", ctxt)))
         vshPrint(ctl, "%s %s", iface, state);
     else
-        vshPrint(ctl, "%s default", iface);
+        vshPrint(ctl, "%s up", iface);
 
     ret = true;