Disable c-bak service in tempest-full* jobs

Cinder backup tests suffer from a high failure rate and
given they do not interact with many other services (glance
and swift for the most part it looks like) we should disable
them from running in the tempest-full job which is part of
the integrated-gate project template, which is what this change
does.

My recommendation would be to make sure cinder backup test
coverage is happening in some other non-integrated-gate jobs
which are running on cinder changes already, like the
cinder-tempest-dsvm-lvm-lio-barbican job (which is voting but
not gating on cinder changes).

This should also help with bug 1783405 where tempest-full
can timeout due to backup tests which aren't marked slow.

c-bak was already disabled in tempest-full-py3 because
swift is disabled but this copies the same note to the
tempest-full-py3 job definition.

Change-Id: I9d39d9d7d706ba3fcba5ff352e8c9e31ab4639a2
Related-Bug: #1483434
Related-Bug: #1745168
Related-Bug: #1783405
Related-Bug: #1813217

.zuul.yaml

@@ -100,6 +100,13 @@
       devstack_localrc:
         ENABLE_FILE_INJECTION: true
         ENABLE_VOLUME_MULTIATTACH: true
+      devstack_services:
+        # NOTE(mriedem): Disable the cinder-backup service from tempest-full
+        # since tempest-full is in the integrated-gate project template but
+        # the backup tests do not really involve other services so they should
+        # be run in some more cinder-specific job, especially because the
+        # tests fail at a high rate (see bugs 1483434, 1813217, 1745168)
+        c-bak: false
 
 - job:
     name: tempest-full-oslo-master
@@ -169,6 +176,12 @@
         s-object: false
         s-proxy: false
         # without Swift, c-bak cannot run (in the Gate at least)
+        # NOTE(mriedem): Disable the cinder-backup service from
+        # tempest-full-py3 since tempest-full-py3 is in the integrated-gate-py3
+        # project template but the backup tests do not really involve other
+        # services so they should be run in some more cinder-specific job,
+        # especially because the tests fail at a high rate (see bugs 1483434,
+        # 1813217, 1745168)
         c-bak: false
 
 - job: