bump diego-ssh
bump diego-ssh

Submodule src/github.com/cloudfoundry-incubator/diego-ssh 603398b..1cc2eb9:
  > Add get-ssh-code to plugin command list

Signed-off-by: Matthew Sykes <fb2dd171fe47bac8d5b55d1d785c243b0892e206@gmail.com>

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release