conversationsview: homogenize temporary item between Gnome and MacOSX

When querying a name in the search bar, we should see:
"Searching..." or "Not found" and the registered name below. Or,
actually, the registered name is not shown for the temporary item.
So, fix patch update the renderer to reflect that.

Change-Id: Idc0061300024820af7fed9fe9eaa45748bf03d0a
Reviewed-by: Hugo Lefeuvre <hugo.lefeuvre@savoirfairelinux.com>