change macro format for source repos
    
    changed from gitN, commitN to git_$repo, commit_$repo to better track what
    macro is used by a repo. Also helps to make things uniform between rhel and
    fedora given that sub-repos enter and leave docker all the time.
    
    also, d-s-s is now renamed to container-storage-setup, so downloaded
    tarball uses the new name.
    
    Signed-off-by: Lokesh Mandvekar <lsm5@fedoraproject.org>