Check AFI/SAFI before comparing them in X509v3_addr_is_canonical()

Check AFI/SAFI before comparing them in X509v3_addr_is_canonical()

As mentioned in a previous commit, IPAddressFamily_cmp() can't really
check for trailing garbage in addressFamily->data. Since the path
validation and hence the X.509 validator call X509v3_addr_is_canonical(),
this deals with only partially validated data.

ok jsing