related log:
2014-04-03 11:42:54,324 [1396525374] Error :   The module Mongodb raised an exception 'Module' object has no attribute 'username', I remove it!
2014-04-03 11:42:54,351 [1396525374] Error :   Back trace of this remove: Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/shinken/modulesmanager.py", line 191, in get_instances
    inst = module.get_instance(mod_conf)
  File "/var/lib/shinken/modules/mod-mongodb/module.py", line 60, in get_instance
    username = plugin.username
AttributeError: 'Module' object has no attribute 'username'