Fix testScreenCaptureDisabled

* A SecurityException was being thrown because getProfiles
  in UserManager cannot be called by the COPE PO for user 0
  without permission MANAGE_USERS or CREATE_USERS.
* Added binderWithCleanCallingIdentity to this method.

Bug: 149941985
Test: atest com.android.cts.devicepolicy.OrgOwnedProfileOwnerTest#testScreenCaptureDisabled
Change-Id: Iccc60233baaeaa732f197d7aaf31acc9d75a247b