[JUnit] More robustness for layout files if member repeated.

Repeating a property member  in the layout.xml results in confusion...

eg, when "bookingIdentifier" was repeated more than once, this is what was observed:

on the booking page we see for example “Collection Address” both on the main panel and in the “Other” panel.

Using the “Rebuild metamodel” menu option the “other" list reduces as expected.  However, it loses the on the Collection location panel.

If I edit the booking identifier on the Misc tab and save then the field disappears until I refresh the page.