This patch refactors a bit the way we add pending surface roles, such
that it updates to an existing surface, rather than create a new one
with the same app_id.
Bug-AGL: SPEC-4133
Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: Ifd7477ea0f0840d6fd82bbc21216a7694d0efa8b