clone_create_ks_distributions.sh won't work for old/new RHEL5 distro naming

[hardys]

RHEL 5 kickstart distribution naming changed between 5u6 and 5.7, https://github.com/hardys/clone_release_scripts/pull/3 makes clone_create_ks_distributions.sh work with the new format, but now it won't work with the old format.

Essentially the previous and current behavior is wrong, and it would be good to add some test which allows us to do the right thing in both circumstances (e.g so clone_release_from_rhel_release.sh will work properly on <5.7)