btrfs: test directory fsync after deleting snapshots

btrfs: test directory fsync after deleting snapshots

Test that if we fsync a directory that had a snapshot entry in it that
was deleted and crash, the next time we mount the filesystem, the log
replay procedure will not fail and the snapshot is not present anymore.

This issue is fixed by the following patch for the linux kernel:

  "Btrfs: fix unreplayable log after snapshot delete + parent dir fsync"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Tested-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>