sqlserver::login create|delete/login.sql.erb not working with AD logins

When using WINDOWS_LOGIN, the login.sql.erb templates are incorrectly checking the sys.sql_logins table instead of sys.server_principals.

Example manifest snippet (NOTE: the '//' in the first line is actually a pair of back-slashes but Jira doesn't like that for somereason):

  sqlserver::login{ "mydomain//foo":

    instance => 'MSSQLSERVER',

    login_type => 'WINDOWS_LOGIN',

    ensure     => 'present',

    svrroles   => { 'sysadmin' => 1, 'serveradmin' => 0, 'processadmin' => 0, 'setupadmin' => 0, 'bulkadmin' => 0, 'diskadmin' => 0, 'dbcreator' => 0, },

    require    => Sqlserver::Database['bar'],

  }

Unfortunately, the error is chomped by Puppet agent runs, but if you copy the generated SQL from such a config into MSSQL Studio you will find the following error on all but the first run:
The server principal 'mydomain\foo' already exists.