monitor: after a scan only trigger a health check if mirror was down
monitor: after a scan only trigger a health check if mirror was down

Previously a health check was done after each successful scan even if the
mirror was checked only few seconds ago.

Myself5/mirrorbits,etix/mirrorbits,Myself5/mirrorbits,etix/mirrorbits,wsnipex/mirrorbits,Myself5/mirrorbits,kib/mirrorbits,etix/mirrorbits,kib/mirrorbits,wsnipex/mirrorbits,wsnipex/mirrorbits,kib/mirrorbits