`hookupVariables` cannot be used in VMs

[DrprofLuigi]

On trailers, hookupVariables cannot be used in VMs.

For example I have a basic VM thatapplies the p_brake lever when either t_brake or !connection_1_1_connected is 1.

		{
			"variable": "p_brake",
			"animations": [
				{
					"animationType": "translation",
					"variable": "t_brake",
					"axis": [0, 0, 1]
				},
				{
					"animationType": "translation",
					"variable": "!connection_1_1_connected",
					"axis": [0, 1, 0]
				}
			],
			"minValue": 0,
			"maxValue": 1
		}

But because t_brake is pulled from the towing truck via hookupVariables, it does not effect this VM.

This also applies to subParts. If a subPart references the brake in animations, lightObjects, etc. it works fine. However when that subpart tries to use brake in a VM, it doesn't work.

For UNU specifically, this also prevents animated suspension from being able to activate.