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/common/test.py b/heat_tempest_plugin/common/test.py
index 429d4ae..34ab24e 100644
--- a/heat_tempest_plugin/common/test.py
+++ b/heat_tempest_plugin/common/test.py
@@ -257,7 +257,7 @@
     def is_service_available(self, service_type):
         try:
             self.identity_client.get_endpoint_url(
-                service_type, self.conf.region)
+                service_type, self.conf.region, self.conf.endpoint_type)
         except kc_exceptions.EndpointNotFound:
             return False
         else: