mdadm: fetch from git

mdadm: fetch from git

Upstream has released a new version (4.4) but not the tarball for it.

Adjust one of the devtool selftests, as it requires that the recipe
under test is using a tarball. Another selftest also needs to be
tweaked to correctly clean up its modifications to that same recipe on
test completion.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>