SSH: Set UserKnownHostsFile to /dev/null

As we are dealing with temporary SSH host keys, we should not pollute the
users's known hosts file with ephermeral data.  Additionally, this avoids
issues where the user has an invalid known hosts file, as in
rancher-sandbox/rancher-desktop#504.

Signed-off-by: Mark Yen <[email protected]>

Author: mook-as

pkg/sshutil/sshutil.go

@@ -155,6 +155,7 @@ func CommonArgs(useDotSSH bool) ([]string, error) {
 
 	args = append(args,
 		"-o", "StrictHostKeyChecking=no",
+		"-o", "UserKnownHostsFile=/dev/null",
 		"-o", "NoHostAuthenticationForLocalhost=yes",
 		"-o", "GSSAPIAuthentication=no",
 		"-o", "PreferredAuthentications=publickey",