Restores to 4.1 and 4.1.1 break with 4.0.1 where SSH keys are on the filesystem

When restoring a snapshot from 4.0.1 onto 4.1 or 4.1.1 where SSH keys on the manager fileystem (e.g in /etc/cloudify/agent_key.pem) have been used for agents on compute nodes, the newly restored deployments will be updated to refer to a stored secret version of the SSH key.
However, it appears that the secret is not actually created.
The SSH key still exists in the snapshot.

This appears to work correctly in 4.0.1 and 4.2.