Remove merge comment, clarify wording, and drop useless return value

[jrconlin]

After #1023, there was some discussion about the second get_uaid call in WebPushRouter.route_notification. This question was clarified, however the comment was determined to vague about what was happening.

In addition, there's a useless bool that was being returned from Message.store_message that could be removed to prevent similar confusion later.