title: Navigation View: checkableBehavior="none" not working on latest version
body: <p>Im using the latest Android Design Support Library and have two groups for my Navigation View, one for fragments where I use <code>android:checkableBehavior="single"</code> and one for Activities like Settings and About where I use <code>android:checkableBehavior="none"</code>.</p>
  
  <p>This worked fine up to version 23.0.1 of the library, now when I just use <code>compile 'com.android.support:design:+'</code> The buttons get checked when selecting.</p>
  
  <p>Is this just a bug in the library or do I have to change something for the new version?
  I can't find anything in the changelog.</p>
  
  <p>menu:
      </p>
  
  <pre><code>&lt;group
      android:id="@+id/main"
      android:checkableBehavior="single"&gt;
      &lt;item
          android:id="@+id/navigation_fragment_1"
          android:icon="@drawable/icon"
          android:title="@string/fragment_1" /&gt;
  &lt;/group&gt;
  
  &lt;group
      android:id="@+id/sub"
      android:checkableBehavior="none"&gt;
      &lt;item
          android:id="@+id/navigation_sub_settings"
          android:title="@string/settings" /&gt;
  
  &lt;/group&gt;
  
  &lt;/menu&gt;
  </code></pre>
  
  <p>layout:</p>
  
  <pre><code>&lt;android.support.v4.widget.DrawerLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:id="@+id/drawer_layout"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:fitsSystemWindows="true"&gt;
  
  &lt;RelativeLayout
      android:id="@+id/layout_main"
      android:layout_width="match_parent"
      android:layout_height="match_parent"&gt;
  
      &lt;include layout="@layout/toolbar" /&gt;
  
      &lt;FrameLayout
          android:id="@+id/content_frame"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:layout_below="@+id/toolbar" /&gt;
  &lt;/RelativeLayout&gt;
  
  &lt;android.support.design.widget.NavigationView
      android:id="@+id/navigation_view"
      android:layout_width="wrap_content"
      android:layout_height="match_parent"
      android:layout_gravity="start"
      app:headerLayout="@layout/drawer_header"
      app:menu="@menu/drawer" /&gt;
  &lt;/android.support.v4.widget.DrawerLayout&gt;
  </code></pre>