Falcon can now daemonize and be spawned by the python client

Summary:
Now you can just run falcon.py -b and it will take care of spawning the daemon if
it is not already started.

Test Plan: See summary

Reviewers: NicolasDP

Reviewed By: NicolasDP

Maniphest Tasks: T18

Differential Revision: http://91.121.199.76/D34