Don't crash a bridge authority on SIGHUP if it's not in the consensus

Fixes bug 2572.

changes/bug2572

@@ -0,0 +1,5 @@
+  o Minor bugfixes:
+    - Don't crash a bridge authority on SIGHUP if it can't force itself
+      into its routerlist.  Fixes bug 2572.
+
+

src/or/router.c

@@ -629,7 +629,7 @@ init_keys(void)
   /* 4. Build our router descriptor. */
   /* Must be called after keys are initialized. */
   mydesc = router_get_my_descriptor();
-  if (authdir_mode(options)) {
+  if (authdir_mode_handles_descs(options, ROUTER_PURPOSE_GENERAL)) {
     const char *m = NULL;
     routerinfo_t *ri;
     /* We need to add our own fingerprint so it gets recognized. */