libglusterfs: Fix memory leaks in fd_lk_insert_and_merge

Change-Id: Id322717b79c5252172811fea259f2073f710a463
BUG: 834465
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/4530
Reviewed-by: Anand Avati <avati@redhat.com>
Tested-by: Anand Avati <avati@redhat.com>