glusterd: Fixed volume-sync in synctask codepath.

Change-Id: I2911d3ac80825310f84c5ba6bd7890e65e1ee219
BUG: 950048
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/4643
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>