Always process responses inside RootResource

The REST API would skip propagation of the requests to the RootResource if
it was a request to the empty resource.

server/core/httprequest.cc

@@ -86,8 +86,11 @@ bool HttpRequest::validate_api_version()
 {
     bool rval = false;
 
-    if (m_resource_parts.size() > 0
-        && m_resource_parts[0] == MXS_REST_API_VERSION)
+    if (m_resource_parts.empty())
+    {
+        rval = true;
+    }
+    else if (m_resource_parts[0] == MXS_REST_API_VERSION)
     {
         m_resource_parts.pop_front();
         rval = true;