Enable unattended-upgrades

We were missing a positive value on
`["apt"]["unattended_upgrades"]["enable"]` to enable it.

Refs #499

site-cookbooks/kosmos-base/recipes/default.rb

@@ -30,6 +30,7 @@ include_recipe 'ntp'
 include_recipe 'kosmos-base::journald_conf'
 include_recipe 'kosmos-base::systemd_emails'
 
+node.override["apt"]["unattended_upgrades"]["enable"] = true
 node.override["apt"]["unattended_upgrades"]["allowed_origins"] = [
   "${distro_id}:${distro_codename}-security",
   "${distro_id}:${distro_codename}-updates"