glusterd: Changing the volume entry table's representation.

Change-Id: Ifd3a20452cc18ec2604aa97776e705b1998be03c
BUG: 903478
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/4518
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>