glusterd: Set op_errstr to error string received from peer

... in case of volume op failure on remote host

Change-Id: I7177dc02369dffa82f217496559532d18b7c7c7a
BUG: 963628
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/5018
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>