Fix for EH receiver timeout while opening

[JamesBirdsall]

The CBSChannel is a shared resource on the MessagingFactory, used by all senders/receivers opened on the same EventHubClient. If a sender/receiver tries to send a token at the same time that the existing session to cbs$ node is closing, then a race can occur which leaves the MessagingFactory in a bad state. New senders and receivers will timeout while trying to open because the auth step stalls:

1. The existing CBS session is closing.
2. CBSChannel.sendToken is called, which calls CBSChannel.innerSendToken, which calls FaultTolerantObject.runOnOpenedObject
3. FaultTolerantObject.runOnOpenedObject detects that the RequestResponseChannel it is wrapping is in state CLOSING, so it decides to create a new one and sets this.creatingNewInnerObject to true, then calls RequestResponseOpener.run, which sees that RequestResponseOpener.isOpened is true and short-circuits, doing nothing at all
4. Later, RequestResponseOpener gets the callback from RequestResponseChannel and sets RequestResponseOpener.isOpened to false
5. Still later, user tries to create a new receiver on the same EventHubClient
6. MessageReceiver tries to create a receive link
   a. First step is to send a token via CBSChannel.sendToken, which chains down to FaultTolerantObject.runOnOpenedObject
   b. FaultTolerantObject.runOnOpenedObject sees that this.creatingNewInnerObject is true (left over from step 3) and just queues the action, assuming it will be handled when the channel is finally opened, but nobody is opening the channel…

This is similar to a previous race condition which was caused by tracking the same state in two different places and the two getting out of sync, but is not the same. In this case, RequestResponseOpener.isOpened tracks more than just the state of the inner RequestResponseChannel, so we don't want to change to just use the state of the RequestResponseChannel. The proposed fix is for RequestResponseOpener.run to also check the state of the inner RequestResponseChannel; if the state is mixed (isOpened is still true but the RequestResponseChannel is CLOSING or CLOSED) then use a continuation to replay the call to run() when the close callback for the existing channel has finished cleanup and set isOpened back to false.

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