Send EXTRA_USER with DevicePolicy lock broadcasts

DeviceAdmins inside profiles may receive broadcasts referring either
to the parent profile or to themselves.

We need a way to differentiate that.

Same commit fixes a bug in DevicePolicyManagerTest where USER_SYSTEM
is returned twice in getProfiles() when called for a managed profile of
USER_SYSTEM. This does not happen in the real API.

Bug: 30185351
Bug: 31001762
Test: runtest -x services/tests/servicestests/src/com/android/server/devicepolicy/DevicePolicyManagerTest.java
Change-Id: Iea2735357f4019b2b81b6784e7ea6aead63f2636