Ansible launcher: don't report result on abort
Ansible launcher: don't report result on abort

When a worker is asked to abort a job, do not send a result to zuul.
If Zuul asked for the abort, Zuul will ignore the result anyway. If
the operator asked for the abort (i.e., by shutting down the launcher)
then the null result will suggest to Zuul it should relaunch the job.

Change-Id: I8ad35e70f76ede31b78c67ebfb0104554b28e8c2

wikimedia/integration-zuul,gooddata/zuul,gooddata/zuul,gooddata/zuul,gooddata/zuul,wikimedia/integration-zuul,gooddata/zuul,wikimedia/integration-zuul,wikimedia/integration-zuul