zypper.CreateTarball() creates backup directory path elements with no permissions

[rtamalin]

While implementing unit tests for PR #229 I noticed that when the CreateTarball() routine creates the var/adm/backup/system-upgrade directory path, in which it will store the backup tarball and restore script, it is specifying no permissions, so the resulting directory path can only be accessed with root privileges.

Given that this code will normally be run as root, this hasn't been a problem up to now, but causes problems for the unit testing.

Using a reasonable permission, e.g. 0o700, that permits at least user access seems like a better approach.

[rtamalin]

@felixsch if a permission of 0o700 is acceptable, that was implemented in #229 so this issue can probably be closed as fixed.