Add org.hibernate.cache to externally marshallable white list

While running 2LC tests I've discovered that some tests fail with:

Caused by: java.lang.AssertionError: Check support for: class org.hibernate.cache.spi.entry.StandardCacheEntryImpl
	at org.infinispan.marshall.core.GlobalMarshaller.writeUnknown(GlobalMarshaller.java:596)

So, org.hibernate.cache.spi.entry.StandardCacheEntryImpl is relying on standard serialization. The problem is that this class does not belong to hibernate-infinispan module and hence cannot be made to extend Infinispan's ExternalPojo.

On the other hand, the white list in ExternallyMarshallable is hardcoded but there are no plans to make this declaratively configurable for now, since the separation between internal and external marshaller will eventually disappear in favour of internal vs user marshaller.

So, the easiest thing to do here would be to add org.hibernate.cache package to the white list.