Report inactive controllers as a diagnostics ok instead of an error (r…

…os-controls#1184)

controller_manager/src/controller_manager.cpp

@@ -2567,7 +2567,7 @@ void ControllerManager::controller_activity_diagnostic_callback(
   }
   else
   {
-    stat.summary(diagnostic_msgs::msg::DiagnosticStatus::ERROR, "Not all controllers are active");
+    stat.summary(diagnostic_msgs::msg::DiagnosticStatus::OK, "Not all controllers are active");
   }
 }