fixed issue with the docs not building due to an issue with ssl library

There was an issue with building the docs, most likely related to this issue: https://github.com/boto/botocore/issues/266 I made a few changes to the Dockerfile, and I got it to work locally.

This was tested by @fredlf who was the original reporter.

@vieux can you test to see if it fixes your issues as well? 
:+1: