title: CardView on Android 5.1 - why show rhombus instead of a circle?
body: <p>I have an CardView with ImageView:</p>
  
  <pre><code>&lt;android.support.v7.widget.CardView
          android:id="@+id/message_avatar_card"
          android:layout_width="40dp"
          android:layout_height="40dp"
          android:layout_marginEnd="4dp"
          android:layout_marginStart="4dp"
          app:cardCornerRadius="40dp"
          android:innerRadius="0dp"
          android:thicknessRatio="1.9"
          android:background="@color/fui_transparent"&gt;
  
          &lt;ImageView
              android:id="@+id/message_avatar"
              android:layout_width="40dp"
              android:layout_height="40dp"
              android:src="@drawable/ic_person_black_24dp"
              android:layout_marginEnd="4dp"
              android:scaleType="centerCrop"
              android:background="@color/fui_transparent"/&gt;
      &lt;/android.support.v7.widget.CardView&gt;
  </code></pre>
  
  <p>On Android 9.0 all is ok, see screenshot</p>
  
  <h2><a href="https://i.stack.imgur.com/H6HjZ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/H6HjZ.png" alt="android 9"></a></h2>
  
  <p>But on Android 5.1 I see rhombus , not circle</p>
  
  <h2><a href="https://i.stack.imgur.com/C2JdQ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/C2JdQ.jpg" alt="android 5.1"></a></h2>
  
  <p><strong>How to fix it?</strong></p>