Extract the .version file when building the srpm file

Extract the .version file when building the srpm file

If you are building the source and binary rpms from a released
tarball, instead of a real git repo, the .version file is required by
build-tools/git-version.  With out this, the version defaults to
UNKNOWN, and although the source rpm will build, it won't compile.

Change-Id: I787b051d5150c65a0d71ac38b30f32e1c560c4b3
Reviewed-on: http://gerrit.openafs.org/2948
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>