Currently rclone allows us to specify the path to a public ssh
certificate file.
That works great for cases where we can specify key path, like local
envs.
If users are using rclone with [volsync](https://github.com/backube/volsync/tree/main/docs/usage/rclone)
there currently is a limitation that users can specify only the rclone config file.
With this change users can pass the public certificate in the same fashion
as they can with `key_file`.
40159e7a16