Avoid re-layout when displaying the page.

Use <span>/<span> instead of <ul>/<il> for task menu anchor, to avoid flickering items when the
menus are created.

app/Template/board/task_menu.php

@@ -1,5 +1,5 @@
-<ul class="dropdown">
-    <li>
+<span class="dropdown">
+    <span>
         <a href="#" class="dropdown-menu"><?= '#'.$task['id'] ?></a>
         <ul>
             <li><i class="fa fa-user"></i> <?= $this->a(t('Change assignee'), 'board', 'changeAssignee', array('task_id' => $task['id'], 'project_id' => $task['project_id']), false, 'task-board-popover') ?></li>
@@ -9,5 +9,5 @@
             <li><i class="fa fa-pencil-square-o"></i> <?= $this->a(t('Edit this task'), 'task', 'edit', array('task_id' => $task['id'], 'project_id' => $task['project_id']), false, 'task-board-popover') ?></li>
             <li><i class="fa fa-close"></i> <?= $this->a(t('Close this task'), 'task', 'close', array('task_id' => $task['id'], 'project_id' => $task['project_id'], 'redirect' => 'board'), false, 'task-board-popover') ?></li>
         </ul>
-    </li>
-</ul>
+    </span>
+</span>