Set a default timeout for sockets
Set a default timeout for sockets

Summary:
We weren't setting a default timeout for socket, which seem to be why we'd have so many accounts randomly dying. This diff does this using `socket.setdefaulttimout()`. We could have used a finer approach (Elasticsales does this by monkey patching `imaplib` inside their fork of `imapclient`) but we need to set a timeout for HTTP and db sockets too.

Test Plan: Tested manually. Checked that setting a timeout didn't break syncs.

Reviewers: emfree, kav-ya

Reviewed By: kav-ya

Projects: #sync-engine

Differential Revision: https://phab.nylas.com/D1630

closeio/nylas,Eagles2F/sync-engine,closeio/nylas,gale320/sync-engine,gale320/sync-engine,nylas/sync-engine,nylas/sync-engine,wakermahmud/sync-engine,gale320/sync-engine,Eagles2F/sync-engine,wakermahmud/sync-engine,jobscore/sync-engine,wakermahmud/sync-engine,ErinCall/sync-engine,ErinCall/sync-engine,ErinCall/sync-engine,nylas/sync-engine,ErinCall/sync-engine,wakermahmud/sync-engine,Eagles2F/sync-engine,jobscore/sync-engine,jobscore/sync-engine,closeio/nylas,wakermahmud/sync-engine,ErinCall/sync-engine,gale320/sync-engine,Eagles2F/sync-engine,closeio/nylas,gale320/sync-engine,Eagles2F/sync-engine,nylas/sync-engine,jobscore/sync-engine