Startcenter: ignore repeated clicks inside recent docs view

(cherry picked from commit 264fc270a73de32a7a4d86442c06d14acdd14ef2)

Conflicts:
	sfx2/source/control/recentdocsview.cxx

Change-Id: Ia433adb26e820b89c4d207d018d0daf42654b4a0
Reviewed-on: https://gerrit.libreoffice.org/7375
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Reviewed-by: Andras Timar <andras.timar@collabora.com>