JCache improved concurrency of CacheManager and CacheProvider impls

CacheManager and CacheProvider removed sync
CacheRecordStore improved checkstyle
CacheStatistics added to ICache and impl for server mode
I'm not fully aware of the threading model of the cache provider; so perhaps I'm missing something.

But this looks like a potential race problem. If 2 threads at the same time execute this method, it can be that 2 HazelcastClients are created. I don't think that is intended behaviour.