gsyncd / geo-rep: overload rename with an unlink

This is certainly a "hack" for cases when after a rename
the gfid is unlinked (which is now pointed by a different
pargfid/basename). This was osbserved when a file edited
(uisng vi/vim) on the glusterfs mount point which has a
geo-replication session running.

Change-Id: I0a5d9f0f549aa4403671fa1f11e95510142e5720
BUG: 1003800
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Tested-by: Amar Tumballi <amarts@redhat.com>
Reviewed-on: http://review.gluster.org/5755
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>