Fixes bug where next/prev would exit fullscreen mode

Next/prev caused an attach() call which in turn
replaced the lightbox elements with themselves
causing the browser to exit fullscreen mode
because the full screened element was shortly
removed from the DOM (to be replaced by the same content),

Unfortunately this cannot be covered by a test case
because the screen would have to truly go into fullscreen
mode for the bug to happen. Having QUnit go fullscreen
seems unreasonable both for local testing (annoying)
and automated testing (could fail  to really fo fullscreen
because user confirmation is requested by the browser).

Change-Id: I57a2668179d6749188d7b5a3efcd06216b7747a9
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/139
Merge "Fixes bug where next/prev would exit fullscreen mode"