Install Guides: Edits based on Anne's comments

Revert and fix some changes as commented on in:
https://review.openstack.org/#/c/60493

Change-Id: Id6355a84bdfeed43a4d2b9657df8745cbc80c632
backport: havana
(cherry picked from commit 4ca6211269fa4165da5a18a8f67bd32d32c4c04e)
Merge "Install Guides: Edits based on Anne's comments" into stable/havana