glusterd/snapshot: Fixed errmsg and Quorum check in Snapshot Operation

1) Removing the static message "unbarrier brick opfailed" and log
errors / message in places.
2) Calling the Snapshot Volume Quorum check if the commit
is passed, as the check(which checks the sanity of
glusterds or snapvolume) a successful commit makes more sense.

Change-Id: I7b8f77aa9b2e553893a6ae71bd4b5bbbb60ab8f1
BUG: 1112559
Signed-off-by: Joseph Fernandes <josferna@redhat.com>
Reviewed-on: http://review.gluster.org/8158
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
Reviewed-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Krishnan Parthasarathi <kparthas@redhat.com>