run-task.py should exit with correct code

[yifanfu]

We are having the issue where task exit with non zero value but the script still exit with code 0. I believe this isn't the correct behaviour as in most of case we need to fail the pipeline if the task is failed. If somehow developers need to keep the pipeline running they should catch that exit code and continue.

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[lzrocha]

Looks good! Thanks for taking the time @yifanfu