Update logic to choose manifest from manifest list to check
for os version on Windows. Separate the logic for windows
and unix to keep unix logic the same.
Signed-off-by: Derek McGowan <derek@mcgstyle.net>
Windows base layers are no longer the special "layers+base" type, so we can remove all the special handling for that.
Signed-off-by: Stefan J. Wernli <swernli@microsoft.com>
