TranscriptLogger does not flush in the event of a SendActivity exception

[tracyboehrer]

This self corrects eventually. Low priority.

Using TranscriptLoggerMiddleware and FileTranscriptLogger

Notes:
TurnContext.SendActivities only logs if the SendActivitiesThroughAdapter succeeds. It would be theoretically possible that some of the Activities were sent before a send exception happens. But the exception would cause none of the Activities to be logged. So, this is a bit worse that described.