[tests/base] Fix for thread issue in tests.
[tests/base] Fix for thread issue in tests.

Summary: See the note on base.py regarding threading vs. monkey patch issue.
More importantly, my tests don't seem to be hanging anymore, however 3 of the
tests are currently / still failing? I'm looking into those now, but thought
I'd provide this diff as a heads-up on progresson the issue.

Test Plan: review the link in base.py

Reviewers: emfree

Subscribers:

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