Updated ScaleoutMessageBus to enable queuing of messages.
- When the backplane goes down it can indicate a disconnect to the
  base class so that it queue any new sends. It can also indicate when
  the connection is back alive so that the queue can be released.
Limited the task queue when the connection is down.
- Extended task queue functionality to enable a hard limit.
- Return failed task when the queue is full.
Fixed fxcop issue.