Compute schedulers in nova - weights section is out of date

[Matt Riedemann]

- [x] This doc is inaccurate in this way:

This bug is specifically about the weights section here:

https://docs.openstack.org/nova/rocky/admin/configuration/schedulers.html#weights

There are a few issues:

1. Mentioning cells in here is not qualified as only for cells v1, which is deprecated. We should either note that the mention of cells weights in that section are for cells v1, or just remove them to avoid confusion.

2. The "Host weighting options" section lists several options with their now deprecated config option group:

https://docs.openstack.org/nova/rocky/admin/configuration/schedulers.html#id15

For example, ram_weight_multiplier is now in the [filter_scheduler] group rather than the [DEFAULT] group. We should fix the groups and link to the actual config option docs using the :oslo.config:option:`<group.name>`_ formatting (or just replace the table with descriptions to a list of related options) - or just drop the table and for each option, document it in the section about the filter/weigher that actually uses that option so there is context.

3. We should probably link to https://docs.openstack.org/nova/rocky/user/filter-scheduler.html#weights which actually explains the various in-tree weighers.

-----------------------------------
Release: 18.0.4.dev13 on 2018-11-24 17:12
SHA: 5d9dd1f63fe940479cfa43afffc369eb8e586050
Source: https://git.openstack.org/cgit/openstack/nova/tree/doc/source/admin/configuration/schedulers.rst
URL: https://docs.openstack.org/nova/rocky/admin/configuration/schedulers.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/rocky
Review: https://review.opendev.org/754349

[OpenStack Infra (hudson-openstack)]

Change abandoned by Harshavardhan Metla (<email address hidden>) on branch: stable/rocky
Review: https://review.opendev.org/754349
Reason: Changed in master in another commit

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/754365