Skip managed profile user test when the target is automotive

- In Auto, some targets don't support FEATURE_MANAGED_USERS.
- The others support the feature, but it is reserved for
passenger user. So, creating another managed profile user is not possible.
- So, it would be needed to skip tests which temporarily creates a
managed user in UserManagerTest.java.
- The correction condition to skip the tests in automotive is
1) not headless system user mode OR 2) not passenger enabled.
- Knowing whether passenger is enabled needs a dependency to car
service, which is not recommended. And, so far, all automotive targets
use headless system user. This CL checks 1) condition.

Bug: 148540026
Test: atest
FrameworksServicesTests: com.android.server.pm.UserManagerTest
Change-Id: I3fe028cc2d9b430546ed02c2fc2e50da870bef58