fix ubuntu build

Author: bbezak

etc/kayobe/kolla.yml

@@ -322,7 +322,7 @@ kolla_build_blocks:
     {% endif %}
   base_ubuntu_package_sources_list: |
     RUN \
-        mv /etc/apt/sources.list{,.backup} && \
+        mv /etc/apt/sources.list /etc/apt/sources.list.backup && \
     {% for repo in stackhpc_ubuntu_focal_repos %}
         echo '{{ repo }}' >> /etc/apt/sources.list {% if not loop.last %} && \
     {% endif %}