locks: fix unconditional op_ret success of entrylk

Bug introduced in recent refactoring. op_ret of entrylk() was always
getting set to 0 even though second locker wouldn't have gotten a lock.
This was resulting in multiple contenders to get locks granted at the
same time.

BUG: 849630
Change-Id: I130d521407afee15de59f270b59687d41982fb29
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/7232
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>