Fix some more failing tests on jenkins

- apps.files.tests.test_models.TestLanguagePack.test_hits_cache,
  apps.files.tests.test_models.TestLanguagePack.test_corrupt_locale_browser_path:
  when migrating to django1.6, forgot to replace this cache timeout of 0 by
  None
- apps.editors.tests.test_sql_model.TestSQLModel.test_values: use UTC dates
- lib.es.tests.test_commands.TestIndexCommand.test_reindexation: add some debug
  log for a test only failing on jenkins, not locally