maintain direct connection

Author: Thomas Reggi

lib/core/sdam/topology_description.js

@@ -151,7 +151,7 @@ class TopologyDescription {
     // update the actual server description
     serverDescriptions.set(address, serverDescription);
 
-    if (serverType === ServerType.Mongos) {
+    if (serverType === ServerType.Mongos && this.s.options.directConnection === false) {
       return new TopologyDescription(
         TopologyType.Sharded,
         serverDescriptions,