Modify igwn alert listener error handling to allow graceful shutdown

I think this MR fixes #554. I think two things were going wrong: One, I think switching from using a context manager (with blah.open() as s) to opening and closing the stream_obj had a little thinko, specifically I think the stream_obj just needed to be closed in the receiver's stop method instead of going in and trying to manually stop that object's private consumer object. Secondly, I think when the stream object is closed in the stop method, the try except clause in the while self.running loop needs to catch it the error and just pass to let the while loop exit (similar to what we found in !1278 (merged))