tracker-controller: Be direct when Tracker can't be found

... so that the problem is more obvious to non-technical end-users.

#120
3 jobs for uajain/tracker-not-found-error in 24 minutes and 41 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #166003
flatpak

00:22:42

 
  Review
passed #166004
review

00:01:59

manual #166005
allowed to fail manual
stop_review