ISPN-4444 After state transfer, a node is able to read keys it no longer...

... owns from its data container

* mark the keys stored as L1
* this avoid read the keys that are going to be invalidated during the ST

https://issues.jboss.org/browse/ISPN-4444
@galderz what do you think about wrapping the metadata in our own? Could this break stuff in the REST server that relies on extended metatada?

TBH I'd rather have a new `L1InternalCacheEntry` extending `MetadataMortalCacheEntry` instead.