Add a hint to the sudo-mode prompt

services/web/app/views/sudo_mode/sudo_mode_prompt.pug

@@ -37,3 +37,9 @@ block content
 													ng-disabled="confirmPassword.inflight"
 												)
 													span #{translate("confirm")}
+
+								.row
+									.col-md-8.col-md-offset-2
+										p.text-centered
+											small
+												| Tip: You are entering "sudo mode", we won't ask for your password again for a while.