cts.py should return a proper exit code to the shell so that wrapper scripts (e.g. continuous.sh) can determine whether the test was successful or not.
 

cts.py should return a proper exit code to the shell so that wrapper scripts can determine whether the tests were performed successfully or not. If tests were executed properly, the return code should be success regardless the actual test result. 

Failures include:
* Errors in building test images
* Errors in flashing images
* Exceptions raised by cts.py