RedHat: fix makesrpm.pl version discovery

We stopped defining the OpenAFS version in AM_INIT_AUTOMAKE a while
back. Use git-version script instead.

Change-Id: I56ef9792cf653921161e177a7c6f143a4b41ace2
Reviewed-on: http://gerrit.openafs.org/8908
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Tested-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>