Don't assume notifications will always be in the topic prefix

[mtwomey]

1. The topic prefix (KAFKA_TOPIC_PREFIX) should work when undefined (e.g. if there is no prefix, the application should still work)

2. "notifications" should not be assumed to be the prefix (guessing we'll have to update Connect here, because it's probably relying on that). Probably tc-bus-api doens't need to be updated regarding this notificaitons prefix, but Connect probably does.
   

[gondzo]

1. ok
2. 'notifications' prefix is in fact added by the event bus - that's just a way for us to keep track of topics in kafka that are related to notifications - there is no other specific use for it

[mtwomey]

@sachin-maheshwari I think you fixed this the week before I came out to India. Please confirm and close if it's fixed. Thanks!

[sachin-maheshwari]

Issue has been addressed in PR - #6