ipautil.backup_file function sees ample use in the service installer code. Its implementation, however, is rather unfortunate: it does move the respective file to a backup, destroying the original in the process.

This means that all attributes and SELinux labels are lost and the caller of this function must constantly re-create the original perms/labels after modifications.

We should create a backup copy of the file instead so that the attributes of the original are preserved in the modified version.