When a client is evicted by a server, it will cancel all locks cached on the client lock namespace and all cached data will be discarded.

In the original implementation, the client will flush the subtree level by level when the root WBC EX lock protected it is revoking.

Instead, during the client eviction, when cancel a WBC EX lock (in the lock blocking callback), the client will discard the whole subtree protected this lock if the import of this lock is in EVICTED state.