Fix perma walk for certain mobs being held hostage

If you target something like a cyborg, that can't change walk intents on the screen like a human can with 'walk allowed' then the mob won't be able to change back to run without typing it. Not a lot of people know what the command for that even is. This fix will simply tell people to change the intent themselves.

Please help me test it, I don't know how to test it alone.
span (see https://github.com/d3athrow/vgstation13/pull/1753/files#r19374576)