Call getPasswordComplexity on the parent profile

Previously, this API did not support explicitly querying the parent profile.
This CL will now allow the WP DPC to call this method since all other password
related methods can already be called.

Screenshot of TestDPC: https://hsv.googleplex.com/4804408720228352 (WP DPC)
                       https://hsv.googleplex.com/5189846769336320

Bug: 138709470
Test: manual testing using Personal and WP TestDPC
      atest com.android.cts.devicepolicy.ManagedProfileTest
      atest com.android.cts.devicepolicy.PasswordComplexityTest
      atest com.android.server.devicepolicy.DevicePolicyManagerTest

Change-Id: I0fb3a96c4469046c8712b5de582c501ea7eb3d8b