Remove call_and_ignore_notfound_exc from helpers unless absolutely necessary

[Felipe Monteiro]

Unless ``call_and_ignore_notfound_exc `` is absolutely needed, it should be avoided as much as possible to avoid suppressing legitimate NotFound exceptions.

See comments by Ghanshyam for context/additional info:

https://review.openstack.org/#/c/457328/15/patrole_tempest_plugin/tests/api/identity/v3/test_domain_configuration_rbac.py

[Ghanshyam Mann (ghanshyammann)]

tracked on story board - https://storyboard.openstack.org/#!/story/1691529