rpc: Close the listener if accept fails.

Change-Id: I5cbd2bfcd08def26903d7b36e550555301a4a16e
diff --git a/runtime/internal/flow/manager/manager.go b/runtime/internal/flow/manager/manager.go
index ae98029..aff1927 100644
--- a/runtime/internal/flow/manager/manager.go
+++ b/runtime/internal/flow/manager/manager.go
@@ -512,6 +512,7 @@
 			close(m.ls.dirty)
 			m.ls.dirty = make(chan struct{})
 		}
+		ln.Close()
 	}()
 	const killConnectionsRetryDelay = 5 * time.Millisecond
 	for {