btrfs: add test for quota disable in parallel with balance

btrfs: add test for quota disable in parallel with balance

Test quota disable during btrfs balance and confirm it does not
cause kernel hang. This is a regression test for the problem
reported to linux-btrfs list [1].

The hang was recreated using the test case and memory backed
null_blk device with 5GB size as the scratch device, and fixed by
kernel patch titled

  btrfs: fix deadlock between quota disable and qgroup rescan worker

[1] https://lore.kernel.org/linux-btrfs/20220115053012.941761-1-shinichiro.kawasaki@wdc.com/

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>