Move docker name to settings.

Change-Id: I2a3679e99ee79f8b12a78e8a90c7dd409daeb309
diff --git a/tcp_tests/managers/openstack_manager.py b/tcp_tests/managers/openstack_manager.py
index 24971b8..89559b1 100644
--- a/tcp_tests/managers/openstack_manager.py
+++ b/tcp_tests/managers/openstack_manager.py
@@ -46,9 +46,8 @@
             conf_name='lvm_mcp.conf',
             registry=None):
         if not registry:
-            registry = ('{}/mirantis'
-                        '/oscore/rally-tempest'
-                        ':latest'.format(settings.DOCKER_REGISTRY))
+            registry = ('{0}/{1}'.format(settings.DOCKER_REGISTRY,
+                                         settings.DOCKER_NAME))
         target_name = [node_name for node_name
                        in self.__underlay.node_names() if target in node_name]