Summary:
Move the `start_systemd_service()` function from `daemon.py` to a separate
module. This allows `daemon.py` to be imported on Windows without causing any
of the systemd logic to be imported.
I kept this separate from the existing `systemd.py` module for now just to
help keep the dependencies a little bit cleaner. The `systemd.py` module
currently does not depend on any other logic from other edenfsctl modules.
Reviewed By: pkaush
Differential Revision: D20854612
fbshipit-source-id: dbdbf0fec90682e3b7d16a7532aefdd3f186bf80
