[Docs] Update from 9.0 to 9.1 should be split up in updating Fuel Master and updating envs

[Sam Stoelinga]

Current update docs: https://docs.mirantis.com/openstack/fuel/fuel-9.1/release-notes/update-product.html tell you how to update Fuel Master and Environments. It's confusing for people just downloading MOS 9.0 and having no existing environments. I suggest to split up the current docs into 2 parts:
1. Updating Fuel Master from 9.0 to 9.1
2. (Optionally) Updating any existing MOS 9.0 environments to 9.1

It should be clear for users that they do not need to do part 2 if they just downloaded MOS 9.0.

Also it would be nice if we could add some command to verify that the update of the fuel master was succesful.

[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: master
Change author: Olena Logvinova <email address hidden>
Review: https://review.fuel-infra.org/28157

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/28157
Submitter: Mariia Zlatkova <email address hidden>
Branch: master

Commit: d9e8bb3b082c9e3bbd76207825a750fd2a128629
Author: Olena Logvinova <email address hidden>
Date: Wed Nov 9 09:50:46 2016

[RN] [Update] Split the Update procedure

This patch:

- splits the Update 9.0 -> 9.1 procedure
  into Master update and Environment update steps
  to cover both new customers with no envs and the
  existing customers with running envs;
- reworks the content to fit the new structure;
- adds a step to check whether the Master update
  was successful.

Change-Id: Id90fa218613e80a6f65303087d3e67f63c939ce3
Closes-Bug: #1638725

[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: stable/9.1
Change author: Olena Logvinova <email address hidden>
Review: https://review.fuel-infra.org/28378

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/28378
Submitter: Mariia Zlatkova <email address hidden>
Branch: stable/9.1

Commit: 637b881091b838271d73fd78ca142c4805433ffe
Author: Olena Logvinova <email address hidden>
Date: Wed Nov 9 15:40:43 2016

[RN] Manual cherry-pick of https://review.fuel-infra.org/#/c/28157

Change-Id: I6777ac2bc724cb59f7f66c3452dea78286595ca7
Closes-Bug: #1638725

[Olena Logvinova (ologvinova)]

The updated instruction is available in both branches now:
https://docs.mirantis.com/openstack/fuel/fuel-9.1/release-notes/update-product.html
https://docs.mirantis.com/openstack/fuel/fuel-master/release-notes/update-product.html

[Alexey. Kalashnikov (akalashnikov)]

Verified on 9.2 snapshot #514