Use F_CLOSEM if available

Use F_CLOSEM to close all file descriptors if available.

BUG: 764655
Change-Id: Ib3c682825b89c163ebb152848f2533b3cb62cdce
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/8379
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Humble Devassy Chirammal <humble.devassy@gmail.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>