overlay, redeploy-links should ignore unknown deployments

When this operation has been first specified, it has been required to fail if the deployment was not existing. That is not right. Linked deployments can be non existing and a pattern can return an empty set of deployments.

The high level operation from the CLI might pass an unexisting deployment name (taking the one from the overlay link to be created for example) which would break the final operation (aka the built composite from the CLI).