Revert change to text on "Add user" page, add an informative popup if a user is modified

deps/rabbitmq_management/priv/www/js/dispatcher.js

@@ -187,8 +187,14 @@ dispatcher_add(function(sammy) {
                    '#/users');
         });
     sammy.put('#/users-add', function() {
-            if (sync_put(this, '/users/:username'))
+            res = sync_put(this, '/users/:username');
+            if (res) {
+                if (res.http_status === 204) {
+                    username = res.req_params.username;
+                    show_popup('warn', "Updated an existing user: '" + username + "'");
+                }
                 update();
+            }
             return false;
         });
     sammy.put('#/users-modify', function() {

deps/rabbitmq_management/priv/www/js/main.js

@@ -1300,7 +1300,9 @@ function sync_req(type, params0, path_template, options) {
         if (type == 'GET')
             return req.responseText;
         else
-            return true;
+            // rabbitmq/rabbitmq-management#732
+            // https://developer.mozilla.org/en-US/docs/Glossary/Truthy
+            return {result: true, http_status: req.status, req_params: params};
     }
     else {
         return false;

deps/rabbitmq_management/priv/www/js/tmpl/users.ejs

@@ -38,7 +38,7 @@
 </div>
 
 <div class="section-hidden">
-  <h2>Add / update a user</h2>
+  <h2>Add a user</h2>
   <div class="hider">
     <form action="#/users-add" method="put">
       <table class="form">
@@ -92,7 +92,7 @@
           </td>
         </tr>
       </table>
-      <input type="submit" value="Add / update user"/>
+      <input type="submit" value="Add user"/>
     </form>
   </div>
 </div>