Add pool_client's methods and tests to Designate tempest plugin

Partially-Implements: blueprint designate-tempest-plugin

Change-Id: Id758b52d30018a7dea363979d167a879a57f09c7
diff --git a/designate_tempest_plugin/clients.py b/designate_tempest_plugin/clients.py
index db1c61f..5edc75a 100644
--- a/designate_tempest_plugin/clients.py
+++ b/designate_tempest_plugin/clients.py
@@ -26,6 +26,8 @@
     ZoneExportsClient
 from designate_tempest_plugin.services.dns.v2.json.recordset_client import \
     RecordsetClient
+from designate_tempest_plugin.services.dns.v2.json.pool_client import \
+    PoolClient
 
 CONF = config.CONF
 
@@ -52,3 +54,5 @@
                                                      **params)
         self.recordset_client = RecordsetClient(self.auth_provider,
                                                 **params)
+        self.pool_client = PoolClient(self.auth_provider,
+                                      **params)