cluster/dht: Create linkfile with file uid/gid

Currently, linkfile creation happens as root.

use uid/gid returned from _cbk (link/rename) to set the correct ownership of
the link files.

Also added test/dht.rc to implement common dht functions

BUG: 884597
Change-Id: I6bc0e04f62d4716fc033681e5678e852a1be7a2f
Signed-off-by: shishir gowda <sgowda@redhat.com>
Reviewed-on: http://review.gluster.org/4607
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>