User switcher - Create user dialog fixes

Make sure the activity is started with the correct user in order to
display properly. Also, the ShadeController is not properly bound in
dagger for non-system users, which was throwing a
NullPointerException. Avoid this and instead use a broadcast to close
the shade.

Fixes: 219638055
Test: atest UserSwitcherControllerTest
Change-Id: I8af80aa10b1bcac92eecdbc65b750a734b2f86ac