Ensure server tests and fixtures properly clean up the global flask app
The global variable vault
gets reused across test runs, so it needs to
be reset on fixture/test teardown, or any potential new config may not
be taken into account, which can in turn generate confusing postgresql
connection closures.
Depends on !141 (closed)
Test Plan
pytest with pytest-random-order
Migrated from D7292 (view on Phabricator)