bcachefs: Kill bch2_path_put_nokeep()

bcachefs: Kill bch2_path_put_nokeep()

bch2_path_put_nokeep() was intended for paths we wouldn't need to
preserve for a transaction restart - it always frees them right away
when the ref hits 0.

But since paths are shared, freeing unconditionally is a bug, the path
might have been used elsewhere and have should_be_locked set, i.e. we
need to keep it locked until the end of the transaction.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>