Align the behaviour of different lock task modes

Currently lock task modes started by the activity flag
android:lockTaskMode behave differently from those started using
startLockTask(). With those changes lock tasks initiated by non-priv
apps cannot finish without calling into stopLockTask. Revoking the
whitelisting on a locked task will also kill that task, independently
of the way the lock task mode was started.

Bug: 21608206
Change-Id: I841abf1103855e2d7218a4a8ca9b43c105630dc9

core/java/android/app/admin/DevicePolicyManager.java

@@ -3976,6 +3976,9 @@ public class DevicePolicyManager {
      * <p>Any packages that shares uid with an allowed package will also be allowed
      * to activate lock task.
      *
+     * From {@link android.os.Build.VERSION_CODES#MNC} removing packages from the lock task
+     * package list results in locked tasks belonging to those packages to be finished.
+     *
      * This function can only be called by the device owner.
      * @param packages The list of packages allowed to enter lock task mode
      * @param admin Which {@link DeviceAdminReceiver} this request is associated with.