Use nested virtualization for CentOS jobs

Change-Id: I1c233505264e0f51f977777253f7634351c70037

zuul.d/nodesets.yaml

@@ -11,13 +11,15 @@
         nodes:
           - controller
 
+
 - nodeset:
     name: devstack-tobiko-centos
     nodes:
       - name: controller
-        label: centos-8-stream
+        label: nested-virt-centos-8-stream
     groups: *STANDALONE_GROUPS
 
+
 - nodeset:
     name: devstack-tobiko-fedora
     nodes:
@@ -62,16 +64,6 @@
           - compute1
           - compute2
 
-- nodeset:
-    name: devstack-tobiko-multinode-centos
-    nodes:
-      - name: controller
-        label: centos-8-stream
-      - name: compute1
-        label: centos-8-stream
-      - name: compute2
-        label: centos-8-stream
-    groups: *MULTINODE_GROUPS
 
 - nodeset:
     name: devstack-tobiko-multinode-fedora