Removed fallback option during getoption on the ConfigManager.
Removed fallback option during getoption on the ConfigManager.

Legacy Python (2.7) ConfigManager does not support the optional argument
fallback when doing a get on the configuration. We are not currently
using it, so until we either sunset Legacy Python support or find a
programmatic workaround we should leave it out.

dubner/pytest-testrail,allankilpatrick/pytest-testrail