If test fails, return a non-zero exit code

This pull request affects unit tests only.
Many unit tests in CondCore/* packages return a zero return value even if the test fails. This causes failures to not be reported as failures in the IB.
In the ROOT 6 IB, there were approximately 15 test failures that were not noticed until now because of this.
NOTE:  Since these code changes are not ROOT 6 specific, they are also being pull requested in the main 7_3_X branch for code commonality.
Please merge this request in the ROOT6 branch as soon as convenient.