ISPN-263 Handle cluster partitions

https://issues.jboss.org/browse/ISPN-263

I added one more commit with some test fixes.
Is there a reason we don't allow reads for a partially owned key?  If we don't allow writes in this case the data should still be consistent.  However I would agree that a get for a key that we don't own at all should throw an AvailabilityException.