Refine extend_info_for_node's "enough info" check once again.

In d1874b433953f64, we adjusted this check so that we insist on
using routerinfos for bridges.  That's almost correct... but if we
have a bridge that is also a regular relay, then we should use
insist on its routerinfo when connecting to it as a bridge
(directly), and be willing to use its microdescriptor when
connecting to it elsewhere in our circuits.

This bug is a likely cause of some (all?) of the (exit_ei == NULL)
failures we've been seeing.

Fixes bug 25691; bugfix on 0.3.3.4-alpha

changes/bug25691

@@ -0,0 +1,6 @@
+  o Minor bugfixes (client):
+    - When using a listed relay as a bridge, and also using
+      microdescriptors, and considering that relay as a non-bridge in
+      a circuit, consider its microdescriptor as a valid source of information
+      about that relay. Fixes bug 25691; bugfix on 0.3.3.4-alpha.
+

src/or/circuitbuild.c

@@ -2860,7 +2860,7 @@ extend_info_from_node(const node_t *node, int for_direct_connect)
   const int is_bridge = node_is_a_configured_bridge(node);
   const int we_use_mds = we_use_microdescriptors_for_circuits(get_options());
 
-  if (is_bridge || !we_use_mds) {
+  if ((is_bridge && for_direct_connect) || !we_use_mds) {
     /* We need an ri in this case. */
     if (!node->ri)
       return NULL;