Tell curl to follow redirects when fetching ISO_CHECKSUM_URL
Tell curl to follow redirects when fetching ISO_CHECKSUM_URL

mirrors.kernel.org is redirecting to mirrors.edge.kernel.org, causing
ISO_NAME to be set to an empty string. This resulted in ISO_URL being
set to the wrong value and packer failing to download the iso.

appleby/Lisp-In-Small-Pieces-VM,elasticdog/packer-arch,agt-the-walker/packer-arch