Remove unofficial bare-metal *_networkds variables

* Remove controller_networkds and worker_networkds variables. These
variables were always listed as experimental, unsupported, and excluded
from documentation in anticipation of Container Linux Config snippets
* Use Container Linux Config snippets on bare-metal instead. They
provide safer, more powerful, and more elegant host customization

bare-metal/container-linux/kubernetes/cl/controller.yaml.tmpl

@@ -163,8 +163,6 @@ storage:
             --net=host \
             --dns=host \
             --exec=/bootkube -- start --asset-dir=/assets "$@"
-networkd:
-  ${networkd_content}
 passwd:
   users:
     - name: core

bare-metal/container-linux/kubernetes/cl/worker.yaml.tmpl

@@ -96,8 +96,6 @@ storage:
       contents:
         inline: |
           fs.inotify.max_user_watches=16184
-networkd:
-  ${networkd_content}
 passwd:
   users:
     - name: core