We can't call __wait_on_freeing_inode() with btree locks held; we're
waiting on another thread that's in evict(), and before it clears that
bit it needs to write that inode to flush timestamps - deadlock.

Fixing this involves a fair amount of re-jiggering to plumb a new
transaction restart.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>