Fix document build

[ktbyers]

No description provided.

[ktbyers]

There are a set of issues here:

1. Jinja2 version 3.x has some compatibility issue with markupsafe. Since this is only for docs, I just forced the docs build to use Jinja2 version 2.x and a version of markupsafe that worked with it.
2. py.test version7 changed the behavior of -c such that our "-c /dev/null" that we call in a couple of the .sh scripts in the docs dir no longer worked properly (i.e. the test rootdir was being set to /dev because of this). I temporarily fixed this by forcing py.test version 6.2.5.
3. We have a coupling to napalm-ansible for some of the documentation build. Newer versions of ansible require Jinja2 >= 3.x. So for now, I just forced a somewhat older version of Ansible to be installed. It is only for the doc-build and the tests that are invoked there.

This at least gets docs building again.

I might try to improve on some of this (in the future), but let's at least do this so docs are building (and we are back in a known working state).