Concurrent access and removal of an AtomicMap should result in an IllegalStateException

Currently, we see:

tx.begin();
Map<?,?> map = AtomicMapLookup.getAtomicMap(cache, key);
assert map.size() == 3;
AtomicMapLookup.removeAtomicMap(cache, key);
assert map.size() == 0;
tx.commit();

Access to the map after its removal is invalid, since even storing data here would be lost.

An IllegalStateException should be thrown if one attempts to access or manipulate an AtomicMap after the AtomicMap has been removed from the cache, since this represents a stale handle.