fix(teardown): properly destroy a topology when initial connect fails

Fixes NODE-1595

Author: daprahamian

lib/mongo_client.js

@@ -201,8 +201,9 @@ MongoClient.prototype.close = function(force, callback) {
   if (typeof force === 'function') (callback = force), (force = false);
 
   // Close the topology connection
-  this.topology.close(force);
-
+  if (this.topology) {
+    this.topology.close(force);
+  }
   // Emit close event
   this.emit('close', this);
 

lib/operations/mongo_client_ops.js

@@ -334,16 +334,21 @@ function createServer(mongoClient, options, callback) {
   // Propagate the events to the client
   const collectedEvents = collectEvents(mongoClient, servers[0]);
 
+  const server = servers[0];
+
   // Connect to topology
-  servers[0].connect(options, (err, topology) => {
-    if (err) return callback(err);
+  server.connect(options, (err, topology) => {
+    if (err) {
+      server.close(true);
+      return callback(err);
+    }
     // Clear out all the collected event listeners
-    clearAllEvents(servers[0]);
+    clearAllEvents(server);
 
     // Relay all the events
-    relayEvents(mongoClient, servers[0]);
+    relayEvents(mongoClient, server);
     // Add listeners
-    addListeners(mongoClient, servers[0]);
+    addListeners(mongoClient, server);
     // Check if we are really speaking to a mongos
     const ismaster = topology.lastIsMaster();
 
@@ -388,7 +393,10 @@ function createTopology(mongoClient, topologyType, options, callback) {
 
   // Open the connection
   topology.connect(options, (err, topology) => {
-    if (err) return callback(err);
+    if (err) {
+      topology.close(true);
+      return callback(err);
+    }
 
     assignTopology(mongoClient, topology);
     callback(null, topology);