Subscriber node changes the topic to which it listens

This defect is based on this question: http://answers.ros.org/question/48086/problem-with-subscribing-to-a-topic-that-contains-slash

I have a node that subscribes to /parent/child, which is an unadvertised topic. Then, a publisher comes in on /parent. The node subscriber automagically starts listening to /parent instead of /parent/child.
