md: Don't ignore suspended array in md_check_recovery()

In the Linux kernel, the following vulnerability has been resolved:

md: Don't ignore suspended array in md_check_recovery()

mddev_suspend() never stop sync_thread, hence it doesn't make sense to

ignore suspended array in md_check_recovery(), which might cause

sync_thread can't be unregistered.

After commit f52f5c71f3d4 ("md: fix stopping sync thread"), following

hang can be triggered by test shell/integrity-caching.sh:

1) suspend the array:

raid_postsuspend

mddev_suspend

2) stop the array:

raid_dtr

md_stop

__md_stop_writes

stop_sync_thread

set_bit(MD_RECOVERY_INTR, &mddev->recovery);

md_wakeup_thread_directly(mddev->sync_thread);

wait_event(..., !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))

3) sync thread done:

md_do_sync

set_bit(MD_RECOVERY_DONE, &mddev->recovery);

md_wakeup_thread(mddev->thread);

4) daemon thread can't unregister sync thread:

md_check_recovery

if (mddev->suspended)

return; -> return directly

md_read_sync_thread

clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);

-> MD_RECOVERY_RUNNING can't be cleared, hence step 2 hang;

This problem is not just related to dm-raid, fix it by ignoring

suspended array in md_check_recovery(). And follow up patches will

improve dm-raid better to frozen sync thread during suspend.