Unit test for getBindDeviceAdminTargetUsers

Was meant to write test for bindDeviceAdminServiceAsUser, but
it can't be done without having tests for
getBindDeviceAdminTargetUsers first as bindDeviceAdminService depends
on getBindDeviceAdminTargetUsers.

A bit shocked by we didn't have any managed profile tests in
DevicePolicyManagerTest. Added managed profile support in the CL.

Bug: 32764274

Test: runtest -x frameworks/base/services/tests/servicestests/src/com/android/server/devicepolicy/DevicePolicyManagerTest.java

Change-Id: If412e4f44c3ae998f69e17411f2503a97f80149f