Pin rally container version

The latest version is currently broken. Pinning to an older version
until the issue is resolved.

ansible/kayobe-automation-run-tempest.yml

@@ -5,7 +5,7 @@
   vars:
     results_path_local: "{{ lookup('env', 'PWD') }}"
     rally_image: 'stackhpc/docker-rally'
-    rally_tag: latest
+    rally_tag: v1.4-dev
     rally_image_full: "{{ rally_image }}:{{ rally_tag }}"
     rally_no_sensitive_log: true
     # This ensures you get the latest image if the image is updated