Unblock the CI gate

The Nova collector json schema validation started [1][2] failing after
the jsonschema upper constraint was bumped from 4.17.3 to 4.19.1 [3].

The reason is that jsonschema v4.18.0a1 switched to a reference
resolving library [4], which treats the aggregate "id" as a jsonschema
id and expects it to be a string [5]. For this reason, we're now getting
AttributeError exceptions.

As a workaround, we'll rename the "id" ref element as "host_aggr_id".

Also, the watcher-tempest-multinode job is configured to use Focal,
which is no longer supported by Devstack [6]. That being considered,
we'll switch to Ubuntu Jammy (22.04).

While at it, we're disabling Cinder Backup, which isn't used while
testing Watched. It currently causes Devstack failures since it
uses the Swift backend by default, which is disabled.

[1] https://paste.opendev.org/raw/bjQ1uIdbDMnmA1UEhxLL/
[2] https://paste.opendev.org/raw/bNgxqulBwBLYB7tNhrU4/
[3] ab0dcbdda2
[4] https://github.com/python-jsonschema/jsonschema/releases/tag/v4.18.0a1
[5] c23a5dc1c9/referencing/jsonschema.py (L54-L55C18)
[6] https://paste.openstack.org/raw/bSoSyXgbtmq6d9768HQn/

Change-Id: I300620c2ec4857b1e0d402a9b57a637f576eeb24

.zuul.yaml

@@ -89,7 +89,7 @@
 - job:
     name: watcher-tempest-multinode
     parent: watcher-tempest-functional
-    nodeset: openstack-two-node-focal
+    nodeset: openstack-two-node-jammy
     roles:
       - zuul: openstack/tempest
     group-vars:
@@ -107,6 +107,7 @@
           watcher-api: false
           watcher-decision-engine: true
           watcher-applier: false
+          c-bak: false
           ceilometer: false
           ceilometer-acompute: false
           ceilometer-acentral: false

watcher/decision_engine/model/collector/nova.py

@@ -48,7 +48,7 @@ class NovaClusterDataModelCollector(base.BaseClusterDataModelCollector):
                     "type": "array",
                     "items": {
                         "anyOf": [
-                            {"$ref": HOST_AGGREGATES + "id"},
+                            {"$ref": HOST_AGGREGATES + "host_aggr_id"},
                             {"$ref": HOST_AGGREGATES + "name"},
                         ]
                     }
@@ -98,7 +98,8 @@ class NovaClusterDataModelCollector(base.BaseClusterDataModelCollector):
                                 "type": "array",
                                 "items": {
                                     "anyOf": [
-                                        {"$ref": HOST_AGGREGATES + "id"},
+                                        {"$ref":
+                                            HOST_AGGREGATES + "host_aggr_id"},
                                         {"$ref": HOST_AGGREGATES + "name"},
                                     ]
                                 }
@@ -129,7 +130,7 @@ class NovaClusterDataModelCollector(base.BaseClusterDataModelCollector):
             "additionalProperties": False
         },
         "host_aggregates": {
-            "id": {
+            "host_aggr_id": {
                 "properties": {
                     "id": {
                         "oneOf": [