tests: spurious failure fix in mgmt_v3_locks.t

Change-Id: I7c4599648b5d47d93a447e58c063fab21e8f9ef7
BUG: 1163543
Signed-off-by: Atin Mukherjee <amukherj@redhat.com>
Reviewed-on: http://review.gluster.org/9114
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>
Tested-by: Kaushal M <kaushal@redhat.com>