Remove devel logic from deb.rake

We should never need to specifically enable the devel repos for building
packages. The main repos are sufficient to build any single project/package
(and if they aren't that needs to be addressed by shipping the dependent
project). This commit removes all of the is_rc, is_devel logic from deb.rake.
Remove rc tasks from deb.rake

The general deb tasks are now smart enough to differentiate a final build from
an rc build. The rc tasks have also been deprecated for some time. This commit
removes the rc tasks entirely from deb.rake.
Remove dead code from mock.rake

The mock_arch method and arch variable are never used in mock.rake. This commit
removes them.
Remove rc tasks and logic from mock.rake

The main rpm and mock tasks have been able to differentiate between final and
rc builds for some time now, and the rc tasks have been deprecated for almost
as long. This commit removes the rc/devel logic from mock.rake.
Merge pull request #156 from haus/remove_devel

Remove devel