Fix for not released thread in service_description

The thread that is created in the 'temp_adapter' is never released,
we should use task_manager.stop() to release unnecessary resources.
If not released each connection to service will create a threadpool
that is not detected by the garbage collector.

Story: 28885

Change-Id: I2f237b7b8908d0106c2ad0f1b4b2fbf585c86465

openstack/service_description.py

@@ -199,6 +199,7 @@ class ServiceDescription(object):
                     service_type=self.service_type),
                 category=exceptions.UnsupportedServiceVersion)
             return temp_adapter
+        temp_adapter.task_manager.stop()
         proxy_class = self.supported_versions.get(str(found_version[0]))
         if not proxy_class:
             proxy_class = proxy.Proxy