afterlock: add the callback to the top level lock (issue4608) If 'wlock' is taken, we should add 'afterlock' callback to the 'wlock' instead. Otherwise, running post transaction hook after 'lock' is release but 'wlock' is still taken lead to a deadlock (eg: 'hg update' during a hook). This situation is much more common since: 5dc5cd7abbf5 push: acquire local 'wlock' if "pushback" is expected (BC) (issue4596)