Ceph jobs: re-enable a few c-bak tests, add more jobs

Those tests were disabled when ceph was upgraded
to a newer release (I51c90e592070b99422e692d5e9e97083d93146e8)
because they were failing.
But it seems they are working now, and it is not not trivial
at this point to understand whether something was fixed
in ceph or in cinder, so let's re-enable them.

Also, add a few additional (initially experimental) jobs
to double-check the ceph/c-bak scenario against
the stable branches.

This reverts commit 9d626d0de5
and adds more functionalities.

Change-Id: I033e0dc04f342e27d6266ad412d3cb256787c0e6

.zuul.yaml

@@ -19,6 +19,11 @@
         - cinder-tempest-plugin-lvm-lio-barbican
         - cinder-tempest-plugin-lvm-tgt-barbican
         - cinder-tempest-plugin-cbak-ceph
+    experimental:
+      jobs:
+        - cinder-tempest-plugin-cbak-ceph-victoria
+        - cinder-tempest-plugin-cbak-ceph-ussuri
+        - cinder-tempest-plugin-cbak-ceph-train
 
 - job:
     name: cinder-tempest-plugin-lvm-barbican-base
@@ -75,7 +80,6 @@
       Integration tests that runs with the ceph devstack plugin, py3
       and enable the backup service.
     vars:
-      tempest_exclude_regex: '(VolumesBackupsTest.test_bootable_volume_backup_and_restore|TestVolumeBackupRestore.test_volume_backup_restore)'
       devstack_local_conf:
         test-config:
           $TEMPEST_CONFIG:
@@ -84,13 +88,30 @@
       devstack_services:
         c-bak: true
 
+- job:
+    name: cinder-tempest-plugin-cbak-ceph-victoria
+    parent: cinder-tempest-plugin-cbak-ceph
+    nodeset: openstack-single-node-focal
+    override-checkout: stable/victoria
+
+- job:
+    name: cinder-tempest-plugin-cbak-ceph-ussuri
+    parent: cinder-tempest-plugin-cbak-ceph
+    nodeset: openstack-single-node-bionic
+    override-checkout: stable/ussuri
+
+- job:
+    name: cinder-tempest-plugin-cbak-ceph-train
+    parent: cinder-tempest-plugin-cbak-ceph
+    nodeset: openstack-single-node-bionic
+    override-checkout: stable/train
+
 # variant for pre-Ussuri branches (no volume revert for Ceph),
 # should this job be used on those branches
 - job:
     name: cinder-tempest-plugin-cbak-ceph
     branches: ^(?=stable/(ocata|pike|queens|rocky|stein|train)).*$
     vars:
-      tempest_exclude_regex: ''
       devstack_local_conf:
         test-config:
           $TEMPEST_CONFIG: