For people setting creating Sessions via load_from_conf_options, such as
the OpenStack services, turning on split-loggers needs to be done in a
config file. In order to do that, we need to expose it in the conf
options list.
Don't add it to the argparse options for now - it would just add another
command line option that is less likely to see use.
Change-Id: I106c6acbe306e581d293612630ec810c11d9d61c
Monty Taylor