Enable swift in tempest-slow-py3 job

Swift is ready on py3 since stable/ussuri and we enabled
it in tempest-full-py3 job for stable/ussuri onwards.

This commit does the same for tempest-slow-py3 job also so that
we can run swift slow test in this job.

Change-Id: I7fa41d4272f792d6fd00bece202c44e342dfeb0a
diff --git a/zuul.d/stable-jobs.yaml b/zuul.d/stable-jobs.yaml
index 455e283..852bafb 100644
--- a/zuul.d/stable-jobs.yaml
+++ b/zuul.d/stable-jobs.yaml
@@ -153,3 +153,29 @@
       subnode:
         devstack_localrc:
           ENABLE_VOLUME_MULTIATTACH: true
+
+- job:
+    name: tempest-slow-py3
+    parent: tempest-slow
+    # This job version is with swift disabled on py3
+    # as swift was not ready on py3 until stable/train.
+    branches:
+      - stable/pike
+      - stable/queens
+      - stable/rocky
+      - stable/stein
+      - stable/train
+    vars:
+      devstack_localrc:
+        USE_PYTHON3: true
+      devstack_services:
+        s-account: false
+        s-container: false
+        s-object: false
+        s-proxy: false
+        # without Swift, c-bak cannot run (in the Gate at least)
+        c-bak: false
+    group-vars:
+      subnode:
+        devstack_localrc:
+          USE_PYTHON3: true