meta: get the quick group of xfstests (more or less) passing

[dlrobertson]

Consistently failing test cases:

• [ ] - generic/302
• [ ] - generic/372
• [ ] - generic/422: https://github.com/koverstreet/bcachefs/pull/249
• [ ] - generic/467: https://github.com/koverstreet/bcachefs/pull/282
• [ ] - generic/477: https://github.com/koverstreet/bcachefs/pull/282
• [ ] - generic/563

[dlrobertson]

The idea here is that it would be cool to have the quick group of xfstests passing at least to the point where most of the time the tests pass for a basic test and scratch device.