performance/write-behind: Add test case for fd being marked bad
                          after write failures.

Change-Id: I5a3c27be0ad77b7f2660f45977f9f1f8f34ae31c
BUG: 765473
Signed-off-by: Raghavendra G <raghavendra@gluster.com>
Reviewed-on: http://review.gluster.org/4560
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>