This reverts commit 6c2e1ff80f52b939405fe0c14577c584602ae432.
GNU gzip does not fail when the image filename already contains the .gz
extension, this is a problem specific to pigz. Revert the commit, as we
now gzip the image twice.
Reported-by: Martin Schleier <drahemmaps@gmx.net>
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
858ff4f3e1