Add test config to libcutils_test

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=libcutils_test

Change-Id: Ie083d1641e4ea226cbf7b82c6fd2c115e15b6bf6