Fix starting user in Controls controllers

Before this CL, the starting user was assumed to be 0 (from the
Context). This may not be true if the controllers are instantiated for
the first time while on a secondary user (thanks to Dagger).

This retrieves the correct current user when the controllers are
created.

Test: manual, open Power menu for the first time after switching users
and look at dump
Fixes: 150219351

Change-Id: I69a7ac32b82700feb707972693bd9b672d179f19