Improve HS_ClientManager and fix issue

1.No longer operate HS_Client in homescreen.cpp,move to HS_ClientManager class.
2.In hs_client.cpp,afb_event_push return the count of clients that received the event,
  not push event result, in tap_shortcut/on_screen_message/on_screen_reply directly
  return zero.

Bug-AGL: SPEC-1764

Change-Id: Ief17d3fe3a9c80937fbda05d1c158eeed3924a75
Signed-off-by: wang_zhiqiang <wang_zhiqiang@dl.cn.nexty-ele.com>