Add test config to bootstat_tests

This change allows TradeFederation to run the test directly.
Refer to b/35882476 for design and discussion of this change.

Bug: 35882476
Test: local test
tradefed.sh run template/local --template:map test=bootstat_tests

Change-Id: I3bc2fa19faebe21f6faf8b81e206ea1581918344