Get HMD Worn State does not appear to working as expected for HTC Vive

The Get HMD worn State does not update the worn state when the headset is put on/taken off. Rather it only updates when the headset sleeps or wakes ups. This means that the headset can be taken off/put on without ever updating the worn state.

1. Make sure Vive is hooked up and turned on
2. Create a new VR template project
3. Open project
4. Open level blueprint
5. Use a print string to print out the results from a "Get HMD Worn State" on tick
6. Play in VR preview
7. Put the headset on
   1. Ensure the headset has proper tracking (can see both lighthouses, and everything is solid green the SteamVR device status display).
   2. Make sure the device moves a distance of more than HMDWornMovementThreshold as defined in BaseEngine.ini
8. Pull the headset off
   1. Ensure the headset still has proper tracking (can see both lighthouses, and everything is solid green the SteamVR device status display).
   2. Let the device sit perfectly still for at least 60 seconds (SteamVR does not send the VREvent_TrackedDeviceUserInteractionEnded event until ~60 seconds have elapsed without any movement)

Results: The Heads set only updates when it activates (not when put on or taken off)
Expected: The head set would update the worn state when the headset it put on and when it was taken off