Drivers get the host keys to expect in optional_args["ssh_host_keys"] (by port)
and report what they saw through optional_args["ssh_host_key_observer"].
With a known key, any other key is refused before authentication
(SshHostKeyMismatch); without one, the first key is accepted. One
implementation for paramiko (HostKeyCheck.connect) and netmiko
(HostKeyCheck.netmiko + observe). A caller or driver that ignores both keys
keeps working as before.
Version 4.19.0.
christianmanivong