Changing a user's password doesn't work

[webcompas]

Affected Puppet, Ruby, OS and module versions/distributions

• Puppet: 4.10.9
• Ruby: 2.3.1p112
• Distribution: Ubuntu 16.04
• Module version: 2.0.0

How to reproduce (e.g Puppet code you use)

1. Create a database user

mongodb_user { "foobar":
    username      => 'foo',
    database      => 'bar',
    password      => '12345',
    roles         => ['readWrite'],
  }

2. Change Puppet code to use "abcde" as password
3. Try to authenticate to MongoDB using the new password

What are you seeing

After Step 1 authentication succeeds. But after changing to another password it fails:

root@test:~# mongo -u foo -p abcde bar
MongoDB shell version: 2.6.10
connecting to: bar
2018-02-05T09:35:31.723+0100 Error: 18 { ok: 0.0, errmsg: "auth failed", code: 18 } at src/mongo/shell/db.js:1287
exception: login failed

Trying to authenticate using the previous password works:

root@test:~# mongo -u foo -p abcde bar
MongoDB shell version: 2.6.10
connecting to: bar
>

What behaviour did you expect instead

Authentication using the new password should work.

Any additional information

When running Puppet Agent at step 2 there are no error messages. According to the debug output the password change is done using the following command:
Debug: Executing '/usr/bin/mongo bar --quiet --host 127.0.0.1:27017 --eval load('/root/.mongorc.js'); db.runCommand({"updateuser": "foo","pwd": "abcde","digestpassword": true})'

If I run the command manually I get the error "no such cmd: updateuser":

root@test-pu-mongodb:~# mongo bar
MongoDB shell version: 2.6.10
connecting to: bar
> db.runCommand({"updateuser": "foo","pwd": "abcde","digestpassword": true});
{
        "ok" : 0,
        "errmsg" : "no such cmd: updateuser",
        "code" : 59,
        "bad cmd" : {
                "updateuser" : "foo",
                "pwd" : "bar",
                "digestpassword" : true
        }
}

Comparing the password hash within MongoDB with the expected one shows that it is still using the one for the old password.

[webcompas]

The reason for the error is the wrong spelling of the Mongo command. Instead of updateuser it has to be updateUser.
Additionally Mongo shell 2.6 doesn't support param "digestpassword" (see https://docs.mongodb.com/v2.6/reference/method/db.updateUser/).