test_x509: test very long OID
Active Directory creates OIDs long enough to trigger a failure.
This can cause e.g. ipa-server-install failure when installing
with an externally-signed CA.
https://pagure.io/freeipa/issue/7300
Reviewed-By: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Christian Heimes <cheimes@redhat.com>