Change name of rbac_role_converter to rbac_policy_parser.

This patch simply changes the name of the file and class of
rbac_role_converter/RbacPolicyConverter to the more accurate
name of rbac_policy_parser/RbacPolicyParser, because no "conversion"
is actually performed; instead the policy file is parsed and the
contents of which are passed to oslo_policy, which if anything does
the actual conversion.

Also fixes a bug in the event that an Exception is caught
in rbac_policy_parser: when an Exception is thrown, `rule` is never
defined, resulting in a NameError in _try_rule. `rule` is changed
to `apply_rule` to resolve this.

Change-Id: I978c5134f8ab922b7fb3d9c901c936dee2f62f8b
3 files changed