Fix socket descriptor leak

The connection to amqp was not getting cleaned up, even after the
communication to conductor across amqp was complete, for a given
request. Thus, sockets were leaking with each communication and finally
led to a hang situation, where no more fds were available.

Change-Id: I1deabdbce6ba448fe4c25d7694aabe5e5fec7b5a
Closes-Bug: #1510776

magnum/api/hooks.py

@@ -81,6 +81,9 @@ class RPCHook(hooks.PecanHook):
     def before(self, state):
         state.request.rpcapi = conductor_api.API(context=state.request.context)
 
+    def after(self, state):
+        state.request.rpcapi = None
+
 
 class NoExceptionTracebackHook(hooks.PecanHook):
     """Workaround rpc.common: deserialize_remote_exception.

magnum/common/rpc_service.py

@@ -106,6 +106,9 @@ class API(object):
                                            serializer=serializer,
                                            timeout=timeout)
 
+    def __del__(self):
+        self._client.transport.cleanup()
+
     def _call(self, method, *args, **kwargs):
         return self._client.call(self._context, method, *args, **kwargs)