Add key-sample data to InvalidSample

Now that we have a key-only deserializer, use this to create a
key-only sample for invalid samples that are received. The key
CDR that was in the InvalidSample object is not replaced with
the deserialized key sample (which has the key fields filled in
and the other fields default initialized).

Signed-off-by: Dennis Potman <dennis@zettascale.tech>