[AIRFLOW-3263] Ignore exception when 'run' kills already killed job (#4108)
[AIRFLOW-3263] Ignore exception when 'run' kills already killed job (#4108)

Sometimes when you run tasks from command line you get exit code = 1 due
to race condition (job runner tries to get process group from the
process that has already been terminated in the meantime)
owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow