bcachefs: Go RW earlier, for normal rw mount

Previously, when mounting read-write after a clean shutdown, we wouldn't
go read-write until after all the recovery passes completed.

Now, go RW early in recovery, the same as any other situation we'll need
to go read-write. This fixes a bug where we discover unlinked inodes
after a clean shutdown: repair fails because we're read only.

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