<archive> tag can extract into host file-system

[rkapl]

Problem description

<archive name="etc.tar" target_dir="/etc" /> extract's into host FS.

The documentation correctly gives examples without the leading /, but this is still dangerous and unexpected behavior.

Expected behaviour

It extracts into guest FS, even if the path is absolute.

OS and Software information

• KIWI version: KIWI (next generation) version 9.24.43, seems to be present in master too
• Operating system host version: SUSE Leap 15.5
• Operating system target version: SUSE Leap 15.5

[schaefi]

Really a bad one, thanks for reporting. I'm going to fix it

[schaefi]

After debugging I found that I fixed this problem together with the implementation in #1953

To be absolute sure I added a unit test to test the absolute path condition. So newer versions of kiwi should not have this problem