Use [database]/connection in templates

nova-manage uses the [database]/connection to determine the
database connection. This change updates the nova.conf
template to use the parts/section-database template,
switching away from using [DEFAULT]/sql_connection to use
[database]/connection instead.

[DEFAULT/sql_connection has been deprecated since at least
mitaka:
https://docs.openstack.org/nova/mitaka/sample_config.html

This change also re-enables the gate tests for Xena.

Closes-Bug: #1951874
Change-Id: I9d77b44ad3c40f3ee60fedc3f211f3ac085fcbb2

osci.yaml

@@ -2,18 +2,8 @@
     templates:
       - charm-unit-jobs-py38
       - charm-unit-jobs-py39
-      # focal-xena fails due to:
-      # https://bugs.launchpad.net/charm-nova-cell-controller/+bug/1951874
-      # - charm-xena-functional-jobs
+      - charm-xena-functional-jobs
       - charm-yoga-functional-jobs
-    check:
-      jobs:
-        # focal-xena fails due to:
-        # https://bugs.launchpad.net/charm-nova-cell-controller/+bug/1951874
-        - focal-xena:
-            voting: false
-        - impish-xena:
-            voting: false
     vars:
       needs_charm_build: true
       charm_build_name: nova-cell-controller

src/templates/mitaka/nova.conf

@@ -10,7 +10,7 @@ logdir=/var/log/nova
 state_path=/var/lib/nova
 root_helper=sudo nova-rootwrap /etc/nova/rootwrap.conf
 
-{% include "parts/database" %}
+{% include "parts/section-database" %}
 
 [conductor]
 workers = {{ options.workers }}

src/templates/pike/nova.conf

@@ -12,7 +12,7 @@ root_helper=sudo nova-rootwrap /etc/nova/rootwrap.conf
 
 {% include "parts/section-transport-url" %}
 
-{% include "parts/database" %}
+{% include "parts/section-database" %}
 
 [conductor]
 workers = {{ options.workers }}

src/templates/train/nova.conf

@@ -12,7 +12,7 @@ root_helper=sudo nova-rootwrap /etc/nova/rootwrap.conf
 
 {% include "parts/section-transport-url" %}
 
-{% include "parts/database" %}
+{% include "parts/section-database" %}
 
 [conductor]
 workers = {{ options.workers }}