Skip the user visibility check for private displays

UserManager doesn't track the user visibility for private displays and
it's enough to check if the given uid has the access.

Fix: 338139109
Bug: 312321592
Test: atest CtsCarBuiltinApiTestCases in cf_x86_64_only_auto_md
Test: atest WmTests:DisplayContentTests
Change-Id: I0568a413ada1511543d859649fc0d9e2a370d726