unattended-installer: Use correct cache path

d4bd651 caused a regression, where unattended installation setup failed
for OSes for which we download drivers (win7 and winxp) if the driver
files only exist in system cache since the code still tried to use the
user cache for all situations.

This patches fixes the issue by using the cache where there the file
exists/is downloaded.
Resolve merge conflict in Greek translation file

This should have been in 8f202664dddb50f7ba7abacc718ca5db9d060ce4.