Test an unknown (bogus) payload in an AUTH's SK payload.

In the first exchange both east and west include unknown but
non-critical payloads inside the AUTH SK payload.  Since the payloads
are ignored, the connection establishes.

In the second exchange, west includes a critical unknown payload in
its AUTH SK payload.  East then responds with UNSUPPORTED CRITICAL
PAYLOAD inside the AUTH SK response, and the IKE SA is promptly
deleted.