Convert policy API to flask

Migrate the policy APIs to use flask-native dispatching.

Change-Id: I03fc72b19e85df711b213c1fe47b30b3f9f91d6c
Partial-Bug: #1776504

keystone/server/flask/application.py

@@ -30,11 +30,9 @@ from keystone.auth import routers as auth_routers
 from keystone.common import wsgi as keystone_wsgi
 from keystone.contrib.ec2 import routers as ec2_routers
 from keystone.contrib.s3 import routers as s3_routers
-from keystone.endpoint_policy import routers as endpoint_policy_routers
 from keystone.federation import routers as federation_routers
 from keystone.identity import routers as identity_routers
 from keystone.oauth1 import routers as oauth1_routers
-from keystone.policy import routers as policy_routers
 from keystone.resource import routers as resource_routers
 
 # TODO(morgan): _MOVED_API_PREFIXES to be removed when the legacy dispatch
@@ -48,6 +46,7 @@ _MOVED_API_PREFIXES = frozenset(
      'OS-SIMPLE-CERT',
      'OS-TRUST',
      'limits',
+     'policy',
      'regions',
      'registered_limits',
      'role_assignments',
@@ -65,11 +64,9 @@ ALL_API_ROUTERS = [auth_routers,
                    assignment_routers,
                    identity_routers,
                    app_cred_routers,
-                   policy_routers,
                    resource_routers,
                    federation_routers,
                    oauth1_routers,
-                   endpoint_policy_routers,
                    ec2_routers,
                    s3_routers]