Remove current password from account object result

When updating a user account e-mail address or password, we have to pass along the current password. For example, doing a PUT to ?q=[my-endpoint]/user/123.json with the following data...

{ uid: 123, name: 'Bob', mail: 'bob@hotmail.com', current_pass: 'my_current_secret', pass: 'my_new_secret' }

...results in the current_pass value being present (plain text) in the account JSON object result. Here's a simple patch that removes it.