Fix fips flag handling.

Don't set the fips flags in cipher and digests as the implementations
aren't suitable for FIPS mode and will be redirected to the FIPS module
versions anyway.

Return EVP_CIPH_FLAG_FIPS or EVP_MD_FLAG_FIPS if a FIPS implementation
exists when calling EVP_CIPHER_flags and EVP_MD_flags repectively.

Remove unused FIPS code from e_aes.c: the 1.0.2 branch will never be
used to build a FIPS module.