This is an easy way for us to signal that certain versions are
compatible with each to etcd-manager, which is otherwise
overly-cautious when it comes to unknown versions.
We extend kops-utils to support the `-t` flag (like cp) to write to a
directory; and the `-s` flag (like cp) to use symlinks. The syntax
isn't identical to cp, but should be semi-familiar and allows us to
minimize the number of initContainers we use.