SshTool: delete deprecated transferFileTo/From(...)
Delete deprecated SshTool.PROP_PRIVATE_KEY

- Use PROP_PRIVATE_KEY_DATA instead
Deleted deprecated SshTool.PROP_KEY_FILES
Fix SshjTool.copyToServer retry

- See https://github.com/brooklyncentral/brooklyn/issues/768
Merge pull request #771 from aledsage/fix/SshjTool-copyToServer-retry

Fix sshj tool copy to server retry