Allow instance to be upgraded to another version installed in the cluster.

[simonvane]

What would you like to be added: Allow kubectl kudo upgrade... to be run specifying a version that is already installed in the cluster, without having to specify a set of files in a repo of file share.

Why is this needed:

1. We have access to the cluster but not the repo where the operators are developed.
2. It would be much simpler to call use kubectl get operatorversions find the versions then use a chosen version to upgrade to.
3. The versions installed in the cluster are the "approved versions".