Implement RbacUtilsMixin for base RBAC classes
This PS implements a RbacUtilsMixin mixin class in rbac_utils
module. This mixin is useful for doing basic Patrole setup in one
place. The mixin currently handles skipping tests if the flag
`[patrole] enable_rbac` is False and initializing rbac_utils
for each RBAC test.
Following changes have been made:
* Implementation of RbacUtilsMixin
* Associated unit tests
* Refactor base RBAC classes to use the mixin
* Trivial documentation changes
Change-Id: Ieaf19ccc8ce374b12af4c481a2bddcdbe86dedec
7 files changed