Cleaned up a few more things about the testing configuration now that we've deployed Django 2.2 to production:

* Go back to a single version of django-oauth-toolkit, tox doesn't need to vary it anymore
* Go back to PyPI release of django-method-override
* Remove no longer needed dependency on python-oauth2 (we already removed the package it was used by)
* Update prepare_xdist_nodes.sh with new Django requirements file options

This reverts commit 70600d79.

* Revert "Use pip-sync to make sure that dep cache tarball can go safely stale"

This reverts commit d435f4cd.

* Revert "Extract worker setup into own shell script, as much as possible"

This reverts commit 0a079e75.

This "fixes" egg-links in a really hacky way to compensate for the lack
of a real relocatable virtualenv.

This is not needed in Makefile as
all the logic and invocation of
compilejs would be done via
ecommerce-script repo.

PROD-960

This patch adds compilejs
management command to be executed
on pull translations enabling
availability of js/jsx translations
for  lms/cms code.

PROD-960

Django-auth-toolkit update

Pinned the latest commit from github to get Django2.2 support in testing.
Pinned the zipp<2.0.0 to get Python<3.5 support too.

* Switch make upgrade to Python 3.5

* bok-choy fixes, constrain django-debug-toolbar

* Remove flaky bok-choy test

The API documentation decorators do not have to leak which solution we
use to generate the docs. Here, and as discussed in PR #21820, we rename
the `openapi` module to `apidocs`, and we make sure that this module
includes all the right functions to document API Views without referring
to Open API.

The xblock counting script had a requirements file that was not
previously being tracked and had an out of date version of requests.
Add it to the `upgrade` make target so that it stays up to date.

* Updating Python Requirements

* Don't rely on pip-compile cache

* Fix tornado dependency resolution

job to work even if some resource is not available.

This reverts commit a7fa0c21.

Paver commands were causing requirement problems
running on jenkins so changed to i18n_tools commands
LEARNER-2653

This would fail if the "git clean" step failed, and would not restore
your private files. Running it again would then fail to make an empty
tarball, clobbering the saved private files.  Now we are more resilient
to a number of failure modes.