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

Fixes #6987
Fixes #6939
This will always evaluate to true if the current widget is a fixed header.You need to add `.not( this.element )` also you cant search on the whole document because this will find toolbars in other hidden pages.  It will also fail if we are dealing with a fixed footer rather then a header. instead lets do:

```
hasFixed = $(  "body>.ui-" + this.options.role + "-fixed" ).add( this.pagecontainer.pagecontainer( "getActivePage" ) ).find( ".ui-" + this.options.role + "-fixed" ).not( this.element ).length
```
I'm thinking remove the word children here as they are not always children.