md raid1 can pass down barriers, but does not set an ordered flag on the
queue, so xfs does not even attempt a barrier write, and will never use
barriers on these block devices.

Remove the flag check and just let the barrier write test determine
barrier support.

A possible risk here is that if something does not set an ordered flag and
also does not properly return an error on a barrier write... but if it's
any consolation jbd/ext3/reiserfs never test the flag, and don't even do a
test write, they just disable barriers the first time an actual journal
barrier write fails.

SGI-PV: 983924

SGI-Modid: xfs-linux-melb:xfs-kern:31377a
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Tim Shimmin <tes@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>