Where applicable, modify all repo config filenames to use a dot
to separate the release major and minor version. Modify test cases
to not remove dot from the distro version any more.
Existing tests will be extended (or new tests added) to explicitly test
backward compatibility and ensure that using old distro names without a
dot still works.
Signed-off-by: Tomáš Hozza <thozza@redhat.com>