md: support re-add of recovering devices.

We currently only allow a device to be re-added if it appear to be
in-sync.  This is overly restrictive as it may be desirable to re-add
a device that is in the middle of recovery.

So remove the test for "InSync" - the test on rdev->raid_disk is
sufficient to ensure that the re-add will succeed.
Reported-by: Alexander Lyakas <alex.bolshoy@gmail.com>
Tested-by: Alexander Lyakas <alex.bolshoy@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -5784,8 +5784,7 @@ static int add_new_disk(struct mddev * mddev, mdu_disk_info_t *info)
 			super_types[mddev->major_version].
 				validate_super(mddev, rdev);
 		if ((info->state & (1<<MD_DISK_SYNC)) &&
-		    (!test_bit(In_sync, &rdev->flags) ||
-		     rdev->raid_disk != info->raid_disk)) {
+		     rdev->raid_disk != info->raid_disk) {
 			/* This was a hot-add request, but events doesn't
 			 * match, so reject it.
 			 */