MK8S-25: Fix repository health check after disabling autoindex

Check repomd.xml instead of directory listing since HTTP directory
browsing was disabled for security. The repomd.xml file is the
standard RPM repository metadata that's always present.

Author: rdebay-scality

salt/metalk8s/repo/installed.sls

@@ -97,8 +97,10 @@ Ensure repositories container is up:
 
 Wait for Repositories container to answer:
   http.wait_for_successful_query:
+   # Check repomd.xml instead of directory listing since autoindex is disabled
+   # This RPM repository metadata file is always present and validates repo functionality
    - name: http://{{ grains.metalk8s.control_plane_ip }}:{{
-     repo.port }}/{{ saltenv }}/
+     repo.port }}/{{ saltenv }}/repodata/repomd.xml
    - status: 200
    - request_interval: 1
    - require: