Fix up upgrade order

Correct a faulty comparison between the neutron-gateway
and ovn-chassis charms. The latter is a subordinate
charm. Bring up ovn-dedicated-chassis from the bottom
of the list.

Place nova-compute directly after ovn-central to
reduce OVN control plane downtime. Add an explanatory
admonishment.

Reflect all the above in both the upgrade-charms and
upgrade-openstack pages.

Due to the connection between this documentation and
internal testing, a comment will be added to an existing
zaza-openstack-tests ordering bug (GH #709) explaining
what was done here.

Drive-by: Implement a more efficient build invocation
          by taking advantage of multi-core systems in
          addition to only building changed files.

Related-Bug: #1960275
Change-Id: I18c65bfc333912a480e7942a06641fce3971834e

deploy-guide/source/upgrade-charms.rst

@@ -106,22 +106,22 @@ table.
      - `neutron-api`_
 
    * - 19
-     - `neutron-gateway`_ or `ovn-central`_
+     - `neutron-gateway`_ or `ovn-dedicated-chassis`_
 
    * - 20
-     - `placement`_
+     - `ovn-central`_
 
    * - 21
-     - `nova-cloud-controller`_
-
-   * - 22
-     - `openstack-dashboard`_
-
-   * - 23
      - `nova-compute`_
 
+   * - 22
+     - `placement`_
+
+   * - 23
+     - `nova-cloud-controller`_
+
    * - 24
-     - `ovn-dedicated-chassis`_
+     - `openstack-dashboard`_
 
    * - 25
      - `ceph-osd`_

deploy-guide/source/upgrade-openstack.rst

@@ -318,22 +318,22 @@ charm's OpenStack service will be updated.
      - `neutron-api`_
 
    * - 17
-     - `neutron-gateway`_ or `ovn-central`_
+     - `neutron-gateway`_ or `ovn-dedicated-chassis`_
 
    * - 18
-     - `placement`_
+     - `ovn-central`_
 
    * - 19
-     - `nova-cloud-controller`_
-
-   * - 20
-     - `openstack-dashboard`_
-
-   * - 21
      - `nova-compute`_
 
+   * - 20
+     - `placement`_
+
+   * - 21
+     - `nova-cloud-controller`_
+
    * - 22
-     - `ovn-dedicated-chassis`_
+     - `openstack-dashboard`_
 
    * - 23
      - `ceph-osd`_
@@ -347,6 +347,12 @@ charm's OpenStack service will be updated.
    * - 26
      - `octavia`_
 
+.. note::
+
+   The OVN control plane will not be available between the commencement of the
+   ovn-central upgrade and the completion of the nova-compute upgrade. They are
+   deliberately placed in close proximity to each other for this reason.
+
 .. note::
 
    An Octavia upgrade may entail an update of its load balancers (amphorae) as

tox.ini

@@ -12,5 +12,5 @@ deps = -r{toxinidir}/requirements.txt
 commands = {posargs}
 
 [testenv:deploy-guide]
-commands = sphinx-build -a -W -d deploy-guide/build/doctrees -b html deploy-guide/source deploy-guide/build/html
+commands = sphinx-build -j auto -W -d deploy-guide/build/doctrees -b html deploy-guide/source deploy-guide/build/html
            whereto deploy-guide/source/_extra/.htaccess deploy-guide/test/redirect-tests.txt