Use divingbell-single-node nodeset

Change-Id: I7704225267a006ec687613dbda290ca4284f80ba

.zuul.yaml

@@ -10,6 +10,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- nodeset:
+    name: divingbell-single-node
+    nodes:
+      - name: primary
+        label: ubuntu-focal
+    groups:
+      - name: primary
+        nodes:
+          - primary
+
 - project:
     templates:
       - docs-on-readthedocs
@@ -43,14 +53,14 @@
 - job:
     name: airship-divingbell-linter
     run: tools/gate/playbooks/zuul-linter.yaml
-    nodeset: openstack-helm-single-node
+    nodeset: divingbell-single-node
 
 - job:
     name: airship-divingbell-chart-build-gate
     description: Builds charts using pinned Helm toolkit.
     timeout: 7200
     run: ./tools/gate/playbooks/build-charts.yaml
-    nodeset: openstack-helm-single-node
+    nodeset: divingbell-single-node
 
 - job:
     name: airship-divingbell-chart-build-latest-htk
@@ -58,7 +68,7 @@
     timeout: 7200
     voting: false
     run: ./tools/gate/playbooks/build-charts.yaml
-    nodeset: openstack-helm-single-node
+    nodeset: divingbell-single-node
     vars:
       HTK_COMMIT: master
 
@@ -82,7 +92,7 @@
 - job:
     name: airship-divingbell-ubuntu
     parent: airship-divingbell
-    nodeset: openstack-helm-single-node
+    nodeset: divingbell-single-node
 
 - job:
     name: divingbell-upload-git-mirror