Show executing SQL statement in long-running query log message

Also fix typo ("progess" -> "progress").  Refactor unit test, and add unit test coverage for log message.
I know this sounds like a jerk question, but have you hand-tested this against a running cluster with a real long-running query?  This null value makes me think that you aren't going to get the behavior you expect, since I think this is the call that actually does the real work for MP transactions.