Refactor LXC image expiration

Right now we write output of `date -d @{{ timestamp }} to
the expiry file, and then attempt to comapre with timestamp.
However, output of  `date -d` is datetime and not timestamp,
so these 2 things can not be properly compared. So image cache
was valid forever.

Change-Id: I42f5b43f09d3c530813dd7fd334eafce7a5eaf39

defaults/main.yml

@@ -203,6 +203,10 @@ lxc_hosts_container_build_command: "{{ _lxc_hosts_container_build_command | defa
 # Local path to cached image
 lxc_image_cache_path: "/var/lib/machines/{{ lxc_container_base_name }}"
 
+# Expiration timeout for the cached image
+# Should be in format supported by the to_time_unit filter
+lxc_image_cache_expiration: "1year"
+
 # Set this option to true to pull a new cached image.
 lxc_image_cache_refresh: false
 

releasenotes/notes/fix_lxc_cache_expiration-1656b5758c4ec24e.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    Implemented variable ``lxc_image_cache_expiration`` that controlls for how
+    long cached LXC image will be valid. Default value is `1year`. Variable
+    format should be compatible with community.general.to_time_unit filter.
+fixes:
+  - |
+    LXC image cache expiration mechanism has being fixed. Previously LXC images were
+    valid forever.

tasks/lxc_cache.yml

@@ -16,7 +16,7 @@
 - name: Set LXC cache fact(s)
   set_fact:
     cache_path_fact: "{{ lxc_container_cache_path }}/{{ lxc_cache_map.distro }}/{{ lxc_cache_map.release }}/{{ lxc_cache_map.arch }}/{{ lxc_cache_default_variant }}"
-    cache_time: "{{ ansible_facts['date_time']['epoch'] }}"
+    cache_time: "{{ now().timestamp() }}"
 
 - name: Retrieve the expiry object
   slurp:
@@ -32,7 +32,7 @@
   set_fact:
     lxc_image_cache_refresh: true
   when:
-    cache_time >= (expiry.content|default('MQo=') | b64decode)
+    cache_time | int >= (expiry.content | default('MQo=') | b64decode | int)
   tags:
     - always
 

tasks/lxc_cache_create.yml

@@ -48,21 +48,14 @@
     - expiry
     - templates
 
-- name: Set cache expiry
-  shell: "date -d @{{ (cache_time | int) + 31536000 }}"
-  changed_when: false
-  register: _cache_expiry
-  tags:
-    - skip_ansible_lint
-
 - name: Set expiry
   copy:
-    content: "{{ _cache_expiry.stdout }}"
+    content: "{{ cache_time | int + lxc_image_cache_expiration | community.general.to_seconds | int }}"
     dest: "{{ cache_path_fact }}/expiry"
 
 - name: Set build ID
   copy:
-    content: "{{ cache_time }}"
+    content: "{{ cache_time | int }}"
     dest: "{{ cache_path_fact }}/build_id"
 
 - name: Create base container to use for {{ lxc_container_backing_store }}-backed containers