bcachefs: Don't issue btree writes that weren't journalled

bcachefs: Don't issue btree writes that weren't journalled

If we have an error in the btree interior update path that prevents us
from journalling the update, we can't issue the corresponding btree node
write - we didn't get a journal sequence number that would cause it to
be ignored in recovery.

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