Update mod_pagespeed testing dependency (#1460)

* Update mod_pagespeed testing dependency
(mod_pagespeed commit a7c39a1b5a14f1422fef19e8e9dcb11074ba1c65)
* Add explicit default server{} on secondary_port to so that the recent
tests for css parser improvements land on a vhost with the right filters
enabled.

test/pagespeed_test.conf.template

@@ -88,6 +88,16 @@ http {
   # Expanded to CentralControllerPort directive when RUN_CONTROLLER_TEST=on
   @@CONTROLLER@@
 
+  server {
+    # This is the default vhost for @@SECONDARY_PORT@@
+    # Your request will land here when you pass in an unknown host.
+    listen @@SECONDARY_PORT@@;
+    listen [::]:@@SECONDARY_PORT@@;
+    server_name default.example.com;
+    pagespeed FileCachePath "@@FILE_CACHE@@";
+    pagespeed RewriteLevel CoreFilters;
+  }
+
   server {
     # Sets up a logical home-page server on
     # max-cacheable-content-length.example.com.  This server is only used to