engine: Sync gluster bricks - use server uuid

If server uuid is returned in getVolumesList vdsm
verb, then this is used to identify the server, rather
than the hostname/ip present in brick name.

Also, not adding brick to volume if the brick's server
cannot be resolved.

Change-Id: I2076e77b5415ead7faf6641ce31588333222e70f
Bug-Url: https://bugzilla.redhat.com/1038988
Signed-off-by: Sahina Bose <sabose@redhat.com>