zb: Drop lifetimes from MessageSink
By using synchronous locking. Fortunately, we don't need to maintain a lock on the socket during the only two async method of Sink implementation so we can just always get the lock in these methods.
By using synchronous locking. Fortunately, we don't need to maintain a lock on the socket during the only two async method of Sink implementation so we can just always get the lock in these methods.