Protect against someone changing LabelAccelerator... values.
Protect against someone changing LabelAccelerator... values.

Stackdriver expects the labels to be `make`, `model` and `accelerator_id`.
Currently the tests would keep on passing if someone changed the values of
`LabelAcceleratorMake`, `LabelAcceleratorModel` or `LabelAcceleratorID`. This
makes sure that the tests would fail in that case.

whuwxl/heapster,Stackdriver/heapster,krzyzacy/heapster,piosz/heapster,Stackdriver/heapster,bluebreezecf/heapster,krzyzacy/heapster,whuwxl/heapster,bluebreezecf/heapster,piosz/heapster