Fabric8: container-create-ssh fails when SSH is configured to use ECDSA keys

Issue

container-create-ssh can be configured to use certificate-based authentication between Fabric8 hosts, rather than user/password. A prerequisite, of course, is that SSH is configured this way. Different certification schemes can be supported by using the --private-key switch to locate a specific private key. The default is $HOME/.ssh/id_rsa.

Unfortunately, container creation begins, but then fails, when using an ECDSA key, even when the SSH implementation supports such keys. The error message is simply "Invalid privatekey: XXXXX" (note that 'privatekey' is one word here) where XXXXX is a number that is unlikely to be helpful.