This is in preparation for running it multiple times with different
alignments.
This commit also fixes the fact that we weren't calling mbedtls_aes_free()
on the context (we still aren't if the test fails). It's not an issue except
possibly in some ALT implementations.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Don't use all-bytes zero as a string, it's harder to debug.
This commit uses the test vectors from FIPS 197 appendix C.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
