Only store established connections in the pool

If a connection has not been fully established (i.e. authentication has
been completed) then it should not be considered as a connection pool
candidate.

server/modules/protocol/HTTPD/httpd.c

@@ -81,7 +81,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
         NULL,               /**< Authentication                */
         NULL,               /**< Session                       */
         httpd_default_auth, /**< Default authenticator         */
-        NULL                /**< Connection limit reached      */
+        NULL,               /**< Connection limit reached      */
+        NULL
     };
 
     static MXS_MODULE info =