Fix a bug in the way of killing evobackup.

Fix a bug in the way of killing evobackup.

The process is launched by "run-parts /etc/cron.daily". When you kill the
process, run-parts is not informed and the process go in Z state (and rsync
continue to work!). When another run-parts is launched the part wich kill a
process if already launched fail.

This fix this particular bug.