Add a test to produce into a stream for the 1st time in OnDeactivateAsync

We probably want to add a test case for streams where a grain subscribes to a stream but never produces to it, and then in OnDeactivateAsync is produces to a stream for the 1st time (or calls OnCompletedAsync). That may expose a bug, since we will start a first time producer initialization while deactivating, and this will be followed by producer unregistration as part of DeactivateStreamResources.

Reported https://gitter.im/dotnet/orleans?at=57596f821cf76dd64535887d