mgmt/glusterd: return proper value upon quorum failure in snapshot create

Change-Id: I5474a7cdf03236121bef383955ab403e945cd7ae
BUG: 1101561
Signed-off-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-on: http://review.gluster.org/7961
Reviewed-by: Sachin Pandit <spandit@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>