Fix device intergration test

The suite was broken by aosp/3211875. Because the filegroup does not
use 'proto' directory, the path to the pb2 is now different.

Test: As of aosp/3237630 test_device.py is part of atp so we should
catch breakage faster.
Bug: NA

Change-Id: I9a9b560113320c4ef5115055dc99eaf8e7715260
1 file changed