RedHat packaging: Use %{dist} not %{osver}

RedHat packaging: Use %{dist} not %{osver}

There's a standard mechanism for defining a RPMs target
distribution in the Fedora and RedHat worlds. This is to use the
%{dist} macro, and to insert it at the end (not the beginning) of
the release field.

Move over to using this standard mechanism, and modify the build
system to match. Note that this means that RPM names have now
changed slightly.

Change-Id: I5a4f1ad827223f48658f595ac424ab64fe98ed39
Reviewed-on: http://gerrit.openafs.org/3981
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>