dir auths no longer vote Guard if they're not voting V2Dir

Directory authorities no longer vote in favor of the Guard flag
for relays that don't advertise directory support.

Starting in Tor 0.3.0.1-alpha, Tor clients have been avoiding using
such relays in the Guard position, leading to increasingly broken load
balancing for the 5%-or-so of Guards that don't advertise directory
support.

Fixes bug 22310; bugfix on 0.3.0.6.

changes/bug22310

@@ -0,0 +1,8 @@
+  o Major bugfixes (performance, load balancing):
+    - Directory authorities no longer vote in favor of the Guard flag
+      for relays that don't advertise directory support. Starting in Tor
+      0.3.0.1-alpha, Tor clients have been avoiding using such relays in
+      the Guard position, leading to increasingly broken load balancing
+      for the 5%-or-so of Guards that don't advertise directory support.
+      Fixes bug 22310; bugfix on 0.3.0.6.
+

src/or/dirserv.c

@@ -2266,6 +2266,7 @@ set_routerstatus_from_routerinfo(routerstatus_t *rs,
   rs->is_valid = node->is_valid;
 
   if (node->is_fast && node->is_stable &&
+      ri->supports_tunnelled_dir_requests &&
       ((options->AuthDirGuardBWGuarantee &&
         routerbw_kb >= options->AuthDirGuardBWGuarantee/1000) ||
        routerbw_kb >= MIN(guard_bandwidth_including_exits_kb,