Improve behaviour on fatal errors

If we didn't walk the whole chain, then there may be any kind of errors in the
part of the chain we didn't check, so setting all flags looks like the safe
thing to do.
int mbedtls_x509_crt_parse_file( mbedtls_x509_crt *chain, const char *path )
{
    int ret;
    size_t n;
    unsigned char *buf;

    if( ( ret = mbedtls_pk_load_file( path, &buf, &n ) ) != 0 )
        return( ret );

    ret = mbedtls_x509_crt_parse( chain, buf, n );

    mbedtls_zeroize( buf, n );
    mbedtls_free( buf );

    return( ret );
}

int mbedtls_x509_crt_parse_file( mbedtls_x509_crt *chain, const char *path )
{
    int ret;
    size_t n;
    unsigned char *buf;

    if( ( ret = mbedtls_pk_load_file( path, &buf, &n ) ) != 0 )
        return( ret );

    ret = mbedtls_x509_crt_parse( chain, buf, n );

    mbedtls_zeroize( buf, n );
    mbedtls_free( buf );

    return( ret );
}
