Removed OpenedChannels property

Maintaining the OpenedChannels is very unreliable and led to verifiable memory leaks when using a cached single channel factory.  OpenedChannels is only used to close client channels when the channel factory is closed.  This behavior is not documented by Microsoft as part of the WCF spec, and additionally, seems entirely useless at best, and at worst entirely incorrect: If a car factory builds a car and then the factory closes, do all the cars it built stop running?