glusterd: Made volume-statedump use synctask framework.

Change-Id: I230ecbd8978725070b5910ead4249f21038224a6
BUG: 852147
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/4494
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>