Fix kolla_base_distro check - no more CentOS

Author: markgoddard

etc/kayobe/kolla.yml

@@ -269,7 +269,7 @@ kolla_build_blocks:
     {% endfor %}
   footer: |
     {% if stackhpc_kolla_clean_up_repo_mirrors | bool %}
-    {% if kolla_base_distro == 'centos' %}
+    {% if kolla_base_distro == 'rocky' %}
     RUN \
         tar -xzf /etc/yum.repos.d.backup/repos.tar.gz -C /etc/yum.repos.d && \
         if grep -r '{{ stackhpc_repo_mirror_url }}' /etc/yum.repos.d; then \