Allow to start any timer on timeout

This allows to recur through other timers. Previously timer could only
be self-recurring.
2 jobs for !4 with allow-choice-of-subsequent-timer in 56 seconds (queued for 1 second)
latest detached
Status Name Job ID Coverage
  Build
passed build #6891

00:00:24

 
  Distcheck
passed distcheck #6892

00:00:32