[SCHEMA] Monocle performance.

Summary:
Basic cache.
Monocle's been running this for ~2 days, it's probably the reason
it's been running at all (post the % push).

Only load reqd. Account columns.
This requires the migration + hence cannot be accurately tested on Monocle yet.

Test Plan: Visual.

Reviewers: spang

Differential Revision: https://review.inboxapp.com/D311
Migration update.
Fix to 'cannot acquire gevent lock'.
Revert "Fix to 'cannot acquire gevent lock'."

This reverts commit c526c0bad1bc97ea5c16e5a8f2da7055c7a99243.
Fix to 'cannot acquire gevent lock' (unreverted)

Summary:
service.start_sync() checks if the account's already locked and its sync_state is killed - if so, unlock before trying to
reacquire the lock.

Test Plan: None.

Reviewers: emfree

Differential Revision: https://review.inboxapp.com/D314