shell: Determine the role type

Now that we have the ability to determine the role type between
pop-up diaglos, full-screen, or split ones use the wrappers installed
previously to make use of them.

Keep the same functionality by activating the desktop surface if we
determine we have one.

Bug-AGL: SPEC-3334

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: Ibce3bc040ce3683ab41709d68d5fbf90d90ea539