* OF-1437 Try to stop sessions having their routes removed

This patch adds a lot of debug logging, plus stops the
console NPE'ing when you try to view a detached session.

It also detaches a session before trying to reattach it, to
avoid it being unrouted when the connection is closed.

* OF-1437 Address comments from Guus

* Don't use toString() in debug logging statements.
* Debug log previd and h values.