Always call onProvidersChanged() when packages containing widgets are updated.

- In the existing logic, the call to onProvidersChanged() is called when a package
  with widgets is added or removed, but only called when a package is updated _and_
  there is an app widget bound to a host.  This differs from what the expected
  behavior is based on the documentation and means that packages with widgets that
  update have no way of notifying host apps of changes except via package events.

Bug: 20698931
Change-Id: I60af36d51e99ca1ea751d9d9d03a50ef2d5bef98