Make 3rd party lockscreen widgets work on secondary users

If you install a lockscreen widget app on a secondary user, lockscreen fails to find it.
There were several places where the correct context and userId were required under the
covers - AppWidgetHost, AppWidgetHostView and RemoteViewsAdapter.

Set the user id in the required places and use it to query the package information.

Bug: 7662835
Change-Id: Ife482c8ab2a2e601650b7cfe2660e88d3b8f2050