libglusterfs: Fix memory leaks in fd_lk_insert_and_merge

Change-Id: I666664895fdd7c7199797796819e652557a7ac99
BUG: 834465
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/4525
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>