Prospective distributed-graph fixes and tweaks

These commits are a mix of bugfixes, additional logging statements, and IP address and JGroups message handling tweaks collected during testing with Titan.

I'm unsure whether a8df79d & 2621f8c are implemented in the "Rexster way".  I'll be happy to refactor, given sufficient direction.

2043214 is short but important.  It could be addressed through alternative approaches, but either that commit or a functional equivalent appears necessary to ensure that writes made from the JGroups hint receiver thread become visible to other Rexster threads.

I hope I didn't miss anything major.  I've only tested this locally with Titan + Cassandra on a two VM "cluster".