traymanager: remove all tray icons when unmanaged the selection.

tower:https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/29da88571a804d06af28dcd3c34727e5/
Change-Id: Ic9a3e1e4d96530ea20aee15e1d357719ca5eb689