Better kill implementation

The KILL_JOBS messages send a JOB_KILLED acknowledgment when all the jobs are killed and this is a good thing. But the JOB_COMPLETED message with the COMPLETE_KILLED status for the job is never sent. This event is only sent when the jobs finished before the kill have the time to be execute.

It would be better to have a JOB_COMPLETED for every job even if they were killed, and keep the JOB_KILLED message to be sure that all jobs where killed.