This was found during testing of the fix for:

   https://bugzilla.redhat.com/show_bug.cgi?id=868483

networkValidate was supposed to check for the existence of multiple
portgroups and report an error if this was encountered. It did, but
there were two problems:

1) even though it logged an error, it still returned success, allowing
the operation to continue.

2) It could exit the portgroup checking loop early (or possibly not
even do it once) if a vlan tag was supplied in the base network config
or one of the portgroups.

This patch fixes networkValidate to return failure in addition to
logging the error, and also changes it to not exit the portgroup
checking loop early. The logic was a bit off in the checking for vlan
anyway, and it's intertwined with fixing the early loop exit, so I
fixed that as well. Now it correctly checks for combinations where a
<virtualport> is specified in the base network def and <vlan> is given
in a portgroup, as well as the opposite (<vlan> in base network def
and <virtualport> in portgroup), and ignores the case of a disallowed
vlan when using *no* portgroup if there is a default portgroup (since
in that case there is no way to not use any portgroup).