Mask join tokens in daemon logs

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
(cherry picked from commit e3917c76ce6f75e6c12cd2099d403fdaba8ab218)
Signed-off-by: Tibor Vass <tibor@docker.com>

api/server/middleware/debug.go

@@ -64,7 +64,7 @@ func maskSecretKeys(inp interface{}) {
 	if form, ok := inp.(map[string]interface{}); ok {
 	loop0:
 		for k, v := range form {
-			for _, m := range []string{"password", "secret"} {
+			for _, m := range []string{"password", "secret", "jointoken"} {
 				if strings.EqualFold(m, k) {
 					form[k] = "*****"
 					continue loop0