glpi: Fix missing twisted _parse method

[AnatomicJC]

_parse method was removed from twisted project here: https://twistedmatrix.com/trac/changeset/38812/trunk/twisted/web/client.py

ERROR   cannot import name _parse
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/mmc/agent.py", line 878, in loadPlugin
    plugin = imp.load_module(name, f, p, d)
   File "plugins/glpi/__init__.py", line 31, in <module>
    from mmc.plugins.glpi.config import GlpiConfig
  File "/usr/lib/python2.7/dist-packages/mmc/plugins/glpi/__init__.py", line 34, in <module>
    from mmc.plugins.glpi.provisioning import GlpiProvisioner
  File "/usr/lib/python2.7/dist-packages/mmc/plugins/glpi/provisioning.py", line 27, in <module>
    from mmc.plugins.glpi.auth import GlpiAuthenticator
  File "/usr/lib/python2.7/dist-packages/mmc/plugins/glpi/auth.py", line 29, in <module>
    from twisted.web.client import HTTPClientFactory, _parse, getPage
ImportError: cannot import name _parse
ERROR   Module glpi raise an exception.
glpi not loaded.