Reuse test_app global
In testing @skagan's MRs, I found that we were leaking database connections through multiple calls to TestApp in common/test_helperer/init.py during test suite runs.
This MR can be merged independently of Sam's current MRs as the changes in init.py will provide an immediate reduction in database consumption use.
@mfharris has also created a story in the backlog to see if we can tune our test suite to reduce the creation of multiple sessions and/or database connections.