Change default activation mode to 'Never'

Maintains default behavior of indigo that no controller activation is required.
Enabling required activation can be done by passing 'require_activation' as Always/OnStartup
to the ur_common.launch or by modifying corresponding launch files.

include/ur_modern_driver/ros/service_stopper.h

@@ -14,8 +14,8 @@ enum class RobotState
 
 enum class ActivationMode
 {
-  Always,
   Never,
+  Always,
   OnStartup
 };