This adds a few more things to the upgrade checks
reference docs after getting questions about it
during the Stein release goal implementation from
other project teams:
1. Notes the high level set of steps for upgrading
nova in grenade and where nova-status fits into
that sequence.
2. Links to the oslo.upgradecheck library which
didn't exist when the original document was
written.
3. Adds a FAQs section with Q&A for several things
that have come up during the Stein release goal.
Change-Id: I990e5dbe563fa342f7481c3720445b924447ad54
Story: 2003657
2a25a13ea9