Unregisters the current client. If a client is currently not registered, nothing is done.
The subclass may reset the client instance to null after it has called this method (even if it throws an exception).
true on success or false if no client was registered.
In: Must not be called from within timeout().
See Implementation
Unregisters the current client. If a client is currently not registered, nothing is done.
The subclass may reset the client instance to null after it has called this method (even if it throws an exception).