Move RbacAuthority class into separate module

This patchset simply moves the RbacAuthority abstract base class
into its own module for better code organization.

Change-Id: I89bee142671645f304d622b9e6c25fbab745a7e2
diff --git a/patrole_tempest_plugin/requirements_authority.py b/patrole_tempest_plugin/requirements_authority.py
index 2db12db..683a7eb 100644
--- a/patrole_tempest_plugin/requirements_authority.py
+++ b/patrole_tempest_plugin/requirements_authority.py
@@ -18,7 +18,7 @@
 
 from tempest.lib import exceptions
 
-from patrole_tempest_plugin.rbac_utils import RbacAuthority
+from patrole_tempest_plugin.rbac_authority import RbacAuthority
 
 LOG = logging.getLogger(__name__)