Modify /etc/hosts file to add record to shadow an external url to point to a kubernetes service

• HOSTS_FILE (default: /etc/hosts)
• HOSTS_FILE_BACKUP (default: /etc/hosts.backup)
• LOCK_FILE (default: /var/lock/mirror-hostess)
• SERVICE_NAME (default: registry-mirror)
• SERVICE_NAMESPACE (default: default)
• SHADOW_FQDN (default: registry.example.com)