CacheStatusResponse map uses too much memory

When the cluster is large and there are a log of caches, the CacheStatusResponse map on the new coordinator can get quite large. One of the problems that seems to be that the addresses in DefaultConsistentHash are duplicated on serialization, so the deserialized version occupies more memory.

We need to investigate why the objects are not "shared" by the River marshaller, and maybe work around the problem by de-duplicating the addresses in the externalizer.