set right version value (2) for version 3 certs

see also e8f12c4b

autoca/certutil.py

@@ -44,7 +44,8 @@ def sign_certificate(req, ca_key, ca_crt, serial_num, days,
     cert.set_subject(req.get_subject())
     cert.set_pubkey(req.get_pubkey())
     if extensions:
-        cert.set_version(3)
+        # certificate version 3, not a typo
+        cert.set_version(2)
         cert.add_extensions(extensions)
     cert.sign(ca_key, digest)
     return cert