Fix bug where fingerprint for wrong userId was attempted to be removed.

- cleaned up private API to ensure userId is distinct from groupId.
- fixed bug where we were sending the wrong userId when attempting to
- fix warning about wrong fingerId when receiving final id of 0.

Fixes bug 28268635

Change-Id: Ic8abfbf6fbf173db2d57a76ac2e38b2a71ffd19e

src/com/android/settings/ChooseLockGeneric.java

@@ -651,8 +651,10 @@ public class ChooseLockGeneric extends SettingsActivity {
             if (mFingerprintManager != null && mFingerprintManager.isHardwareDetected()
                     && mFingerprintManager.hasEnrolledFingerprints(userId)) {
                 mFingerprintManager.setActiveUser(userId);
-                mFingerprintManager.remove(
-                        new Fingerprint(null, userId, 0, 0), userId,
+                // For the purposes of M and N, groupId is the same as userId.
+                final int groupId = userId;
+                Fingerprint finger = new Fingerprint(null, groupId, 0, 0);
+                mFingerprintManager.remove(finger, userId,
                         new RemovalCallback() {
                             @Override
                             public void onRemovalError(Fingerprint fp, int errMsgId,