Use configured endpoint instead of hardcoded ones

Usage of public endpoints was hardcoded
- for the Heat client
- in a test for the Zaqar client
- when checking if a service is available

A test also required Heat to be configured to use public endpoints when
talking to services. This test is more relaxed now.

Change-Id: I3784e126d28a51d990702e1b9e6bf23f0447fa21
diff --git a/heat_tempest_plugin/services/clients.py b/heat_tempest_plugin/services/clients.py
index 3999cee..233c2dd 100644
--- a/heat_tempest_plugin/services/clients.py
+++ b/heat_tempest_plugin/services/clients.py
@@ -111,7 +111,7 @@
             self.HEATCLIENT_VERSION,
             endpoint,
             session=session,
-            endpoint_type='publicURL',
+            endpoint_type=self.conf.endpoint_type,
             service_type='orchestration',
             region_name=self.conf.region,
             username=self._username(),