Fixed Toolbar: removing popup removes ui-page-header-fixed class

Fixes #6987
Fixes #6939
@arschmitz  I'm a  bit torn on this one. if the external toolbar is already acting on the page it has been added to the page so `page.children(  ".ui-header-fixed" ).length > 0` should be true even though the header is external right? if not should I be just checking `$.mobile.document.find( ".ui-header-fixed" ).length > 0`