cli: Add `CLI#bye` for exiting with an info msg
cli: Add `CLI#bye` for exiting with an info msg

`CLI#bye` is like `CLI#die`, except that it prints an informational
message instead of an error and exits with a return code of zero instead
of non-zero, signifying success.

woodruffw/kbsecret,kbsecret/kbsecret,kbsecret/kbsecret