glusterd: changes in 'volume create' behaviour

This patch incorporates all the changes suggested on the behaviour of
'volume create' command in http://review.gluster.org/#change,4214
(comment #14, to be precise).

Change-Id: Iaac524a59738b177415595b18aa8a136090d3d25
BUG: 948729
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/4740
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>