glusterd: Made volume-delete use synctask framework.

Change-Id: I52573bb49946f904484e2ead483e8f6f41cbd0c8
BUG: 852147
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/4492
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>