Make sure all tests run in one process

[thomas-maschler]

Is your feature request related to a problem? Please describe.
We have to run tests in two processes right now, to assure the moto mocking environment doesn't interfere with other tests. This messes up the test coverage stats.

Describe the solution you'd like
Either:

• tear down mocking environment when no longer used
  or
• make sure moto tests are run last. this plugin might help, although still in alpha https://pytest-ordering.readthedocs.io/en/develop/