Have transitions in public_server_mode count as affects_descriptor

Previously, we'd get a new descriptor for free when
public_server_mode() changed, since it would count as
affects_workers, which would call init_keys(), which would make us
regenerate a new descriptor.  But now that we fixed bug 3263,
init_keys() is no longer necessarily a new descriptor, and so we
need to make sure that public_server_mode() counts as a descriptor
transition.

src/or/config.c

@@ -3847,7 +3847,8 @@ options_transition_affects_descriptor(or_options_t *old_options,
       !opt_streq(old_options->ContactInfo, new_options->ContactInfo) ||
       !opt_streq(old_options->MyFamily, new_options->MyFamily) ||
       !opt_streq(old_options->AccountingStart, new_options->AccountingStart) ||
-      old_options->AccountingMax != new_options->AccountingMax)
+      old_options->AccountingMax != new_options->AccountingMax ||
+      public_server_mode(old_options) != public_server_mode(new_options))
     return 1;
 
   return 0;