Change control channel handling

Once control method throws exception, channel is closed implicitly.
It means that control channel which is supplied to extension is single
use.

So discard individual class for control channel then create pure channel
every time.

In addition, some interfaces in ServerOperator is removed in order to
reduce amount of created pure channels.
Update tests
Add new methods

Get pure channel instance via RMQManager.
Add checker whether given queue name is already declared or not.