performance/open-behind: Fix fd-leaks in unlink, rename

Change-Id: Ia8d4bed7ccd316a83c397b53b9c1b1806024f83e
BUG: 991622
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5493
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>