override_role cleanup: Remove superfluous call in rbac_rule_validation

This PS cleans up rbac_rule_validation (addressing a TODO) by removing
_override_role call in rbac_utils which is no longer necessary as all
tests have migrated over to override_role.

The call in rbac_rule_validation to _override_role was only needed
to do a role switch to admin role after test execution to compensate
for the limitation in switch_role which did not automatically switch
role via a contextmanager (which is what override_role) does.

Partially Implements: blueprint rbac-utils-contextmanager

Change-Id: I5628886349b22b10b53a3c325fd38bdbaaafafae
1 file changed