DPM.isDeviceOwnerApp() and getDeviceOwner() now check calling user

- Previously on MNC, they would return the same result regardless who
the calling user is.

- Now they properly take DO user-id into account.  Meaning, they'll
always return false and null respectively, if the calling user doesn't
run device owner.

- Note isDeviceOwnerApp() is a public API and getDeviceOwner() is
a system API.  Meaning we're changing the behavior or non-private
APIs.

- Also cleaned up hidden APIs, and gave them explicit suffixes
to avoid confusion.  Bundled code should prefer them for clarity.

Now we have:

* APIs that work cross-users: They all require MANAGE_USERS.
boolean isDeviceOwnerAppOnAnyUser(String packageName)
ComponentName getDeviceOwnerComponentOnAnyUser()

int getDeviceOwnerUserId()
boolean isDeviceOwnedByDeviceOwner()

String getDeviceOwnerNameOnAnyUser()

* APIs that work within user.  No permissions are required.

boolean isDeviceOwnerAppOnCallingUser(String packageName)
ComponentName getDeviceOwnerComponentOnCallingUser()

Bug 24676413

Change-Id: I751a907c7aaf7b019335d67065d183236effaa80