Fix test_CMAC_keygen
Fix test_CMAC_keygen

Make sure we correctly pass through the size of the buffer to
EVP_DigestSignFinal

Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16789)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl