testing: Use identity based CA restrictions in rw-hash-and-url-multi-level

testing: Use identity based CA restrictions in rw-hash-and-url-multi-level

This is a prominent example where the identity based CA constraint is
benefical. While the description of the test claims a strict binding
of the client to the intermediate CA, this is not fully true if CA operators
are not fully trusted: A rogue OU=Sales intermediate may issue certificates
containing a OU=Research.

By binding the connection to the CA, we can avoid this, and using the identity
based constraint still allows moon to receive the intermediate over IKE
or hash-and-url.