Avoid creating user context in a non system user

This change makes it so that when CommunalAppWidgetHostStartable is
started in a non system user and hsum is not enabled, do nothing.

Test: none
Fix: 431515488
Flag: EXEMPT bugfix
Change-Id: I29a44f06e1b73b34d3fed3d59d2712da9b98b877
3 files changed