Add placement API methods for testing routed provider nets

Routed provider networks feature uses the placement API, to test the
feature we need to add the following client methods to the placement
client:
* list_resource_providers
* show_resource_provider
* list_resource_provider_inventories
* list_resource_provider_aggregates

Change-Id: I4e4b104bf4b6b26b02d95b2c9697f4bfdba25ac4
diff --git a/tempest/clients.py b/tempest/clients.py
index 8363a8d..6d19a0c 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -44,7 +44,7 @@
         self._set_object_storage_clients()
         self._set_image_clients()
         self._set_network_clients()
-        self.placement_client = self.placement.PlacementClient()
+        self._set_placement_clients()
         # TODO(andreaf) This is maintained for backward compatibility
         # with plugins, but it should removed eventually, since it was
         # never a stable interface and it's not useful anyways
@@ -139,6 +139,11 @@
         self.snapshots_extensions_client = self.compute.SnapshotsClient(
             **params_volume)
 
+    def _set_placement_clients(self):
+        self.placement_client = self.placement.PlacementClient()
+        self.resource_providers_client = \
+            self.placement.ResourceProvidersClient()
+
     def _set_identity_clients(self):
         # Clients below use the admin endpoint type of Keystone API v2
         params_v2_admin = {