do not ship uncompressed tarballs

There's not much point to shipping uncompressed tarballs in 2013. Delete
them during "make-release".

Change-Id: Ib52bd4a34ef0f5b0eacb973e60f7c1ef921f5ade
Reviewed-on: http://gerrit.openafs.org/10116
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>