If unit 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.
Since these code changes are not ROOT 6 specific, they are being pull requested in the main 7_3_X branch for code commonality.
Fortunately. all the affected unit tests pass in the 7_3_X IB.