Set exit code when unit tests fail

When test_runner.py has any unit tests fail, exits with a non-zero
return code so that test_runner.py can be called from scripts.

Bug: 28321483
Test: Make a unit test fail.  Checked the exit code.
Change-Id: Ib6a9a753d26cd00a4a8785193b03ebb76f7f1d98
1 file changed