fix(mongo-client): ensure close callback is called with client

Author: mbroadst

lib/operations/mongo_client_ops.js

@@ -665,9 +665,9 @@ function generateCredentials(client, username, password, options) {
 
 function closeOperation(client, force, callback) {
   const completeClose = err => {
-    client.emit('close', this);
+    client.emit('close', client);
     for (const name in client.s.dbCache) {
-      client.s.dbCache[name].emit('close');
+      client.s.dbCache[name].emit('close', client);
     }
 
     client.removeAllListeners('close');