In preparation for unifying the AEAD encryption and decryption test
vectors, skip AEAD test vectors with the 'novrfy' (verification failure
expected) flag set when testing encryption rather than decryption.
These test vectors only make sense for decryption.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>