Add some protection from shadowing mount

Currently we do have wrong bind mount order, due to which /var/log/journal
is shadow mounted with later added /var/log mount.
To prevent this we're inserting new mounts before existing ones
in case where they could shadow mount destination.

Change-Id: Id8cca6d83c75202a273df23be353480366ead156
Closes-Bug: #1895533

playbooks/common-tasks/os-lxc-container-setup.yml

@@ -50,6 +50,7 @@
   lineinfile:
     dest: "/var/lib/lxc/{{ inventory_hostname }}/config"
     line: "lxc.mount.entry = {{ item['mount_path'] }} {{ item['bind_dir_path'].lstrip('/') }} none bind,create=dir 0 0"
+    insertbefore: "^lxc.mount.entry = .*\\s{{ item['bind_dir_path'].lstrip('/') | regex_replace('/', '\/') }}.*"
     backup: "true"
   with_items:
     - "{{ lxc_default_bind_mounts | default([]) }}"