cs: return error if starting periodic tasks fails
cs: return error if starting periodic tasks fails

Exit the process if `StartTasks` returns an error.

Closes #4107

GitOrigin-RevId: 569b9f9928ded245002ebdad7ba4c5b9c1ef11f8

netsec-ethz/scion,netsec-ethz/scion,netsec-ethz/scion,netsec-ethz/scion