Fix domain-scope tests for list_domains

A recent change merged in keystone that now allows domain-scoped
tokens to be used to list domains. [1]

This patch changes the tests in the DomainXXXTests classes to expect
the API calls to return without error instead of expecting them to
return 403 - Forbidden.

[1] https://opendev.org/openstack/keystone/commit/dd785ee692118a56ea0e3aaaf7f5bd6c73ea9c91

Change-Id: I97251f7f2974d3c562e59cc461294d9b040193ed
1 file changed