make the tests work

src/test/users-test.js

@@ -10,7 +10,6 @@ const async = require('async'),
     database = require('../database.js'),
     expect = require('expect.js'),
     fs = require('fs'),
-    groupdb = require('../groupdb.js'),
     mailboxdb = require('../mailboxdb.js'),
     maildb = require('../maildb.js'),
     mailer = require('../mailer.js'),
@@ -46,7 +45,6 @@ function cleanupUsers(done) {
     mailer._mailQueue = [];
 
     async.series([
-        groupdb._clear,
         userdb._clear,
         mailboxdb._clear,
     ], done);