bch2_btree_node_get_noiter() isn't used from the btree iterator code,
which retries with the btree node cache cannibalize lock held on
-ENOMEM, so we should do it ourself if necessary.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>