Use python3 devstack ceph plugin job

devstack-plugin-ceph-tempest job is py2 job and
not supposed to run on master gate. We need to use
its py3 version- devstack-plugin-ceph-tempest-py3

Change-Id: I1a817c8dc0d01292bdd89cd46caa094d1ecdad01
diff --git a/.zuul.yaml b/.zuul.yaml
index cfb739d..df01cbf 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -5,7 +5,7 @@
     check:
       jobs:
         - cinder-tempest-plugin-lvm-lio
-        - devstack-plugin-ceph-tempest
+        - devstack-plugin-ceph-tempest-py3
 
 - job:
     name: cinder-tempest-plugin-lvm-lio