Getting baseURL for JMS messages from event user data field, which is set using by HTTP API from UriInfo baseURL

Fixes https://www.pivotaltracker.com/story/show/72351918
Because this will be triggered with each update to the repository, my thinking was that it should fail as quickly as possible.  If an exception is thrown in the try block, it's likely going to happen every time and the baseURL would never be set successfully.  So my thinking was to try once and then not retry if it doesn't work.