Correct return code has to be sent from the Litmus-Service to the Keptn control plane

[jetzlstorfer]

After the tests/chaos experiment in the Litmus Service is finished, the service sends our "pass" as the actual return value.

This has to be improved:

• If the chaos experiment fails, the result should be "fail".
• If the chaos experiment is stopped or interrupted, the result should be "fail".
• If the chaos experiment is successful, the result should be "pass".

Another improvement we should think of is to include the actual result data that is collected by Litmus when sending back the TestsFinished event.