Summary: The module initialization process is complex and full of race conditions. This diff adds a set of unit tests that verify that modules setup happens in the correct order, and enforces all the various conditions for main/background init.
Reviewed By: javache
Differential Revision: D2994145
fb-gh-sync-id: 92ea84508cdeeb280ff0fb9e9b2dffa8dbc37e66
shipit-source-id: 92ea84508cdeeb280ff0fb9e9b2dffa8dbc37e66
