Make apt key import for Ubuntu a uniform process

In https://review.openstack.org/588962 the implementation
of the apt key store copy into the container was changed
for bionic, but left alone for xenial. This patch makes
the approach uniform across both distributions.

Change-Id: I79f49fd02be3bbee5f22cdde000b19578167e3ca

handlers/main.yml

@@ -84,11 +84,6 @@
     name: it_does_not_matter
     daemon_reload: yes
 
-- name: Remove generated apt keys from LXC host
-  file:
-    path: /root/repo.keys
-    state: absent
-
 - name: Remove rootfs archive
   file:
     path: "/tmp/{{ cache_basename }}"

tasks/lxc_cache_preparation.yml

@@ -69,23 +69,6 @@
           to ensure they're available otherwise disable the quota system by
           setting `lxc_host_machine_quota_disabled` to true.
 
-- block:
-    - name: Generate apt keys from LXC host for the container cache
-      shell: "apt-key exportall"
-      changed_when: false
-      register: _apt_exportall
-      tags:
-        - skip_ansible_lint
-
-    - name: Write exported keys to temporary file
-      copy:
-        content: "{{ _apt_exportall.stdout }}"
-        dest: "/root/repo.keys"
-      notify:
-        - Remove generated apt keys from LXC host
-  when:
-    - ansible_pkg_mgr == 'apt'
-
 # NOTE(cloudnull): We're using rsync  and an if block because we've no means
 #                  to loop over a block. Re-evaluate this task when/if this is
 #                  merged https://github.com/ansible/ansible/issues/13262

templates/prep-scripts/ubuntu_16_prep.sh.j2

@@ -5,8 +5,6 @@ set -e -x
 
 {% include 'templates/prep-scripts/_container_sys_setup.sh.j2' %}
 
-apt-key add -v /root/repo.keys
-rm /root/repo.keys
 export DEBIAN_FRONTEND=noninteractive
 apt-get remove -y --purge snap* lxc* lxd* resolvconf* || true
 

vars/ubuntu-16.04.yml

@@ -22,10 +22,10 @@ _lxc_cache_map:
   copy_from_host:
     - /etc/apt/sources.list
     - /etc/apt/apt.conf.d/
+    - /etc/apt/trusted.gpg.d
     - /etc/apt/preferences.d/
     - /etc/environment
     - /etc/localtime
-    - /root/repo.keys
     - /etc/protocols
 
 _lxc_cache_prep_template: "prep-scripts/ubuntu_16_prep.sh.j2"