md/raid1: really fix recovery looping when single good device fails.

Commit 4044ba58 supposedly fixed a
problem where if a raid1 with just one good device gets a read-error
during recovery, the recovery would abort and immediately restart in
an infinite loop.

However it depended on raid1_remove_disk removing the spare device
from the array.  But that does not happen in this case.  So add a test
so that in the 'recovery_disabled' case, the device will be removed.

This suitable for any kernel since 2.6.29 which is when
recovery_disabled was introduced.

Cc: stable@kernel.org
Reported-by: Sebastian Färber <faerber@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/raid1.c

@@ -1161,6 +1161,7 @@ static int raid1_remove_disk(mddev_t *mddev, int number)
 		 * is not possible.
 		 */
 		if (!test_bit(Faulty, &rdev->flags) &&
+		    !mddev->recovery_disabled &&
 		    mddev->degraded < conf->raid_disks) {
 			err = -EBUSY;
 			goto abort;