storage: Check for valid fc_host parent at startup

storage: Check for valid fc_host parent at startup

https://bugzilla.redhat.com/show_bug.cgi?id=1160565

If a 'parent' attribute is provided for the fchost, then at startup
time check to ensure it is a vport capable scsi_host. If the parent
is not vport capable, then disallow the startup. The following is the
expected results:

error: Failed to start pool fc_pool
error: XML error: parent 'scsi_host2' specified for vHBA is not vport capable

where the XML for the fc_pool is:

    <pool type='scsi'>
      <name>fc_pool</name>
      <source>
        <adapter type='fc_host' parent='scsi_host2' wwnn='5001a4aaf3ca174b' wwpn='5001a4a77192b864'/>
      </source>
...

and 'scsi_host2' is not vport capable.

Providing an incorrect parent and a correct wwnn/wwpn could lead to
failures at shutdown (deleteVport) where the assumption is the parent
is for the fchost.

NOTE: If the provided wwnn/wwpn doesn't resolve to an existing scsi_host,
      then we will be creating one with code (virManageVport) which
      assumes the parent is vport capable.

Signed-off-by: John Ferlan <jferlan@redhat.com>