Calling start/stop listening in onStart/onStop

AppWidgetHost in N was changed to make start/stop lisenting calls
light weight, which allows launcher to avoid getting unnecessary
updates when its not visible

Bug: 23892701
Change-Id: I0ca6e02400992bc4e0359e45a3d66b9252751402
(cherry picked from commit 23ac9cb3e1bed8de0155f1a117739a582cb8abae)
2 files changed