cloud-init: disable the /etc/hosts upgrade on boot

The configuration is only applied if a cloudinit_enabled fact is present

Related to T2655

Test Plan

If the fact if present:

diff origin/production/objstorage0.internal.staging.swh.network current/objstorage0.internal.staging.swh.network
*******************************************
+ File[/etc/cloud/cloud.cfg.d/99_modules.cfg] =>
   parameters =>
     "content": "# Managed by Puppet (class profile::cloud-int), changes will be ...
     "ensure": "present",
     "group": "root",
     "mode": "0644",
     "notify": "Service[cloud-init]",
     "owner": "root"
*******************************************
+ Service[cloud-init] =>
   parameters =>
     "enable": true,
     "ensure": "running"
*******************************************
*** End octocatalog-diff on objstorage0.internal.staging.swh.network

no changes if not

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Migrated from D6861 (view on Phabricator)