Switch deployment pipeline's e2e tests to new python3 version

[pjenvey]

Follow up to #911:

Ops' jenkins pipeline runs the now old e2e tests from server-syncstorage's repo as a spot check for deployment. With them now ported to Python 3 and moved to reside in the syncstorage-rs repo, the pipeline needs to switch to running them from there, likely via syncstorage-rs's docker.

Ops needs to switch this themselves but let's ensure:

• it works as expected running from our docker
• we log an issue for ops to change it providing them w/ the correct docker cmd line args

Bonus points for making it as seamless to run as server-syncstorage's docker (which is provided by its custom entrypoint). Otherwise running it by manually overwriting the entrypoint via cmd line args should suffice.

[ethowitz]

Jira

[pjenvey]

Bumping this from a 3 to at least a 5.

syncstorage's own local e2e test suite (test_storage.py) can be invoked via run.py -- in theory from the existing docker image with a custom entrypoint of /app/tools/integration_tests/run.py with an argument pointing to the url of the canary instance (including the secret as a url fragment). However run.py wants to invoke a local instance of the syncserver.

So we need to add a lightweight version that soley runs the e2e tests, possibly with a __main__ function in test_storage.py itself like the older Python 2 version had.

We now also have a tokenserver test_e2e.py test suite which we should be able to point towards a canary instance via the TOKENSERVER_HOST env variable. However it's much more intertwined with FxA in order to produce auth tokens needed for tokenserver requests. Some of the associated values are hardcoded towards FxA stage (e.g. referencing a FXA_ACCOUNT_STAGE_HOST value) so I'm not entirely sure this suite as is could work in our jenkins pipeline against production.