DummyInMemoryStore should respect fetch arguments on process method.

The DummyInMemoryStore currently ignores the fetchValue and fetchMetadata keys. We should make this respect both independently so it can be easier to find if something is broken in a test. An example might be that someone passes fetchValue as false, but they really do require the value and DummyInMemorystore would return the value either way and the caller would still pass even though if they used a different store implementation it might fail.