Use Event_ShowWindow instead of Event_TapShortcut

Use Event_ShowWindow instead of Event_TapShortcut

The interface of homescreen service will be changed then,
use Event_ShowWindow instead of Event_TapShortcut.
Related changes:
  agl-service-homescreen: https://gerrit.automotivelinux.org/gerrit/#/c/17929/
  libhomescreen: https://gerrit.automotivelinux.org/gerrit/#/c/17931/
  libqthomescreen: https://gerrit.automotivelinux.org/gerrit/#/c/17933/

BUG-AGL: SPEC-1931

Change-Id: Ia8e100483fd1a418789483169c815847d2b64b11
Signed-off-by: wang_zhiqiang <wang_zhiqiang@dl.cn.nexty-ele.com>