This change aim to refactor the way of doing the minor upgrade
via ansible playbook download by the config download
It will depend on a mistral change which will get the
ansible update_task and run it via mistral
The user will have two ways for performing the minor update:
- the stack update command which will make an automatic minor
upgrade (or just upgrade a given set of nodes)
- running it manually via ansible on the undercloud
Closes-Bug: #1715557
Closes-Bug: #1723108
Change-Id: I4fcd443d975894a1da0286b19506d00682c5768c