kmod-debian-aliases: Fix source tarball URL.

The original URL for this package was pointed at a location that wasn't
longterm-stable, and has by now been removed by Debian.
This commit fixes the URL to point at a debian snapshot entry, which should
stick around for the long run.

Hash is unchanged, so this is safe.

pkgs/os-specific/linux/kmod-debian-aliases/default.nix

···
   version = "22-1.1";
 
   src = fetchurl {
-    url = "mirror://debian/pool/main/k/kmod/kmod_${version}.debian.tar.xz";
+    url = "http://snapshot.debian.org/archive/debian/20160404T220610Z/pool/main/k/kmod/kmod_${version}.debian.tar.xz";
     sha256 = "0daap2n4bvjqcnksaayy6csmdb1px4r02w3xp36bcp6w3lbnqamh";
   };