Ignore errors for "install available update" Ansible task (#213)

* Ignore errors for "install available update" Ansible task

* Do not fail when update_result is not defined

ansible/roles/system-updater/tasks/softwareupdate.yml

@@ -24,8 +24,10 @@
   # > ssh: connect to host [...] port 22: Connection refused.
   ignore_unreachable: yes
   # Ignore SIGTERM/SIGKILL sent "softwareupdate" process
-  # when the system reboots due to --restart
-  failed_when: update_result.rc not in [0, 9, -9, 15, -15]
+  # when the system reboots due to --restart and any other errors,
+  # since we'll check whether the update was installed in main.yml
+  # anyway.
+  ignore_errors: yes
   become: yes
   loop: "{{ software_updates }}"
   when: "not item.label.startswith('macOS') or item.version.split('.')[0] == ansible_facts['distribution_version'].split('.')[0]"
@@ -38,6 +40,4 @@
     # the commands below on a non-restarted system.
     delay: 60
     timeout: 1800
-  when:
-    - update_result is defined
-    - not update_result.skipped
+  when: update_result is defined and not update_result.skipped | default(false)