whenever a resource adds a field (which is allowed in our API
guidelines), OSC functional tests fail, because we validate
the resource keys to a hardcoded list.
instead, this change proposes that the logic of
assert_show_fields is flipped around, so our hardcoded list acts
as a minimum set of values that must appear in the resource.
as part of this change, some fields were remove from the constants
since they were not actually in the returned data.
also, delete unused code `assert_show_structure`.
Change-Id: I8c0f0e80ea472f9c7f93c5f1f0ae52048e6cd7da
42ac82b1a4