add build for packstack rhel rpm

So here is a patch to get packstack building in firestack.
Let me know if this will work for now..

Couple notes..
I was using a version as its generated by tito for each git tag.  I'll
have to change this, but for now the version is wrong.  I'd assume we'd
want the git hash in the version.  I'll poke around to see how other
rpm versions are derived 

I was not 100% sure where to put this rake task.. rhel.rake seemed like
an ok place, but move it as needed. This should work for fedora too, but
I have not yet tested it. 

I have a workaround in the patch that we should be able to drop if I
can get some changes pushed upstream.