cluster/afr: Fix fd/memory leak on fsync

Change-Id: I764883811e30ca9d9c249ad00b6762101083a2fe
BUG: 976800
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5248
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>