Why do bridges run the retry_dns callback?

In a4fcdc5d, the following roles seem inconsistent:

+  CALLBACK(retry_dns, PERIODIC_EVENT_ROLE_ROUTER),
+  CALLBACK(check_dns_honesty, PERIODIC_EVENT_ROLE_RELAY),

It's probably unrelated, but I don't think clients write stats:

+  CALLBACK(write_stats_file, PERIODIC_EVENT_ROLE_ALL),

(Do onion services write stats?)