title: Popover: Toolbar within ion-header doesn’t stay fixed
body: <p>I have a Popover with a title and a close-button, which should stay fixed on top of the popover. To accomplish this I placed the ion-toolbar within an ion-header tag, which should make it stay fixed in its location (as stated by the docs about Toolbars). But when the content needs scrolling, the toolbar behaves like content and scrolls out of view.</p>
  
  <p><strong>The template of my popover:</strong></p>
  
  <pre><code>&lt;ion-header &gt;
      &lt;ion-toolbar position="top"&gt;
          &lt;ion-button (click)="close()" slot="start" icon-only fill="clear"&gt;
              &lt;ion-icon name="arrow-round-back"&gt;&lt;/ion-icon&gt;
          &lt;/ion-button&gt;
          &lt;ion-title&gt;{{TACName}}&lt;/ion-title&gt;
      &lt;/ion-toolbar&gt;
  &lt;/ion-header&gt;
  &lt;ion-content &gt;
      &lt;ion-card  *ngIf="cardTitle" &gt;
          &lt;ion-card-title  class="card-title"&gt;{{cardTitle}}&lt;/ion-card-title&gt;
      &lt;/ion-card&gt;
      &lt;ion-card *ngIf="cardDesc" &gt;
          &lt;ion-card-title  class="card-desc"&gt;{{cardDesc}}&lt;/ion-card-title&gt;
      &lt;/ion-card&gt;
  &lt;/ion-content&gt;
  </code></pre>
  
  <p>Any ideas how to make the toolbar stay fixed on top of the popover?
  thanks!</p>