Use code-block instead of double-colon + indent

The new sphinx style assumes that indented examples preceded by a
double-colon are python. This changes he main walkthrough page so it
uses a bash code-block in these areas, to be more accurate.
Merge pull request #13821 from terminalmage/docs

Use code-block instead of double-colon + indent
Fixing pylint violations
Merge branch 'develop' of https://github.com/saltstack/salt into create-docker-push-state