Changed UMS so it resolve null names for all users on HSUM.

Prior to this change, it would only resolve it for system, main,
and guest users, which would be confusing for HSUM devices that
don't set the initial user as the main user.

Fixes: 432508642
Test: atest FrameworksMockingServicesTests:UserManagerServiceMockedTest
Test: adb shell dumpsys user |grep 'Unnamed user name'
Flag: android.multiuser.create_initial_user

Change-Id: I62a63051bc8fb6bd03a4d20acba0afff38433089