Make runners.sh actually work (on Jessie)
Make runners.sh actually work (on Jessie)

Debian keeps `systemctl` in `/bin`, CentOS/RHEL keeps it in `/usr/bin`. CentOS/RHEL symlinks `/bin` to `/usr/bin`, so this change enables Jessie compatibility.
pixelrebel/st2,dennybaa/st2,punalpatel/st2,Plexxi/st2,tonybaloney/st2,lakshmi-kannan/st2,pixelrebel/st2,nzlosh/st2,nzlosh/st2,Plexxi/st2,dennybaa/st2,tonybaloney/st2,lakshmi-kannan/st2,lakshmi-kannan/st2,peak6/st2,emedvedev/st2,nzlosh/st2,pixelrebel/st2,StackStorm/st2,armab/st2,StackStorm/st2,StackStorm/st2,emedvedev/st2,armab/st2,dennybaa/st2,armab/st2,tonybaloney/st2,peak6/st2,Plexxi/st2,nzlosh/st2,punalpatel/st2,emedvedev/st2,StackStorm/st2,Plexxi/st2,punalpatel/st2,peak6/st2