md: close some races between setting and checking sync_action.

When checking sync_action in a script, we want to be sure it is
as accurate as possible.
As resync/reshape etc doesn't always start immediately (a separate
thread is scheduled to do it), it is best if 'action_show'
checks if MD_RECOVER_NEEDED is set (which it does) and in that
case reports what is likely to start soon (which it only sometimes
does).

So:
 - report 'reshape' if reshape_position suggests one might start.
 - set MD_RECOVERY_RECOVER in raid1_reshape(), because that is very
   likely to happen next.

Signed-off-by: NeilBrown <neilb@suse.com>

drivers/md/raid1.c

@@ -3113,6 +3113,7 @@ static int raid1_reshape(struct mddev *mddev)
 
 	unfreeze_array(conf);
 
+	set_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
 	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 	md_wakeup_thread(mddev->thread);