btrfs: snapshot creation with qgroup inherit would mark qgroup inconsistent

btrfs: snapshot creation with qgroup inherit would mark qgroup inconsistent

Test that a new snapshot created with qgroup inherit passed should
mark qgroup numbers inconsistent.

Such inconsistent flag is required to show that we need a qgroup
rescan to make qgroup numbers correct again.

This is unavoidable since snapshot creation with qgroup inherit acts
as snapshot creation + qgroup relationship assign.

See btrfs(5) for why such operation needs qgroup rescan.

This test failed on current kernel, the fix is submitted to the btrfs
mail list titled:

  "btrfs: qgroup: Mark qgroup inconsistent if we're inherting snapshot to a new qgroup"

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>