Correct revocation event test for domain_id

The revocation event test used "user_domain_id" and
"project_domain_id" as token fields that the "domain_id"
revocation event field maps to, but the token fields are
actually "identity_domain_id" and "assignment_domain_id", as
can be seen in
keystone.contrib.revoke.model.build_token_values().

Change-Id: I208484da243403287eaa33893d57429c7e6d27c7
Partial-Bug: #1349597
Merge "Correct revocation event test for domain_id"