Check for IP address change every minute, not 15 minutes

Relays used to check every 10 to 60 seconds, as an accidental side effect
of calling directory_fetches_from_authorities() when considering doing
a directory fetch. The fix for bug 1992 removes that side effect. At the
same time, bridge relays never had the side effect, leading to confused
bridge operators who tried crazy tricks to get their bridges to notice
IP address changes (see ticket 1913).

The new behavior is to reinstate an every-60-seconds check for both
public relays and bridge relays, now that the side effect is gone.

changes/bug1992

@@ -4,3 +4,8 @@
       answer in some cases. Fixes bugs 1992 (bugfix on 0.2.0.20-rc)
       and 2410 (bugfix on 0.1.2.2-alpha).
 
+  o Minor features:
+    - Make bridge relays check once a minute for whether their IP
+      address has changed, rather than only every 15 minutes. Resolves
+      bugs 1913 and 1992.
+

src/or/main.c

@@ -1407,7 +1407,7 @@ run_scheduled_events(time_t now)
  * that would require an upload? */
 #define CHECK_DESCRIPTOR_INTERVAL (60)
 /** How often do we (as a router) check whether our IP address has changed? */
-#define CHECK_IPADDRESS_INTERVAL (15*60)
+#define CHECK_IPADDRESS_INTERVAL (60)
 
   /* 2b. Once per minute, regenerate and upload the descriptor if the old
    * one is inaccurate. */