Add buildah to the releng composers.

This commit adds the buildah package to the releng
composer machines so that we can use it to generate the
manifest lists.

See Releng PR: https://pagure.io/releng/pull-request/10249.

Signed-off-by: Clement Verna <cverna@tutanota.com>

playbooks/groups/releng-compose.yml

@@ -163,9 +163,11 @@
   # this is how you include other task lists
   - import_tasks: "{{ tasks_path }}/motd.yml"
 
-  - name: install skopeo for container management
+  - name: install skopeo and buildah for container management
     package:
-      name: skopeo
+      name:
+        - skopeo
+        - buildah
     tags:
     - containerrebuild