ISPN-263 Handle cluster partitions

https://issues.jboss.org/browse/ISPN-263

I added one more commit with some test fixes.
This description seems wrong.  Shouldn't it return true if it has all the data?  Also I noticed the implementation returns true if data is missing which is inverse of this as well.

This made looking at the DegradedModePartitionHandlingStrategy equally confusing because we do a rebalance if not all data is available, which seems wrong.