Remove duplicate bitmaps from Notification parcels

Created when the notification is marshalled and then unmarshalled
across process boundaries, since there are multiple references to the
same image from different places and they all get sent as separate
objects.

Fix: 70152868
Test: make FrameworksCoreTests -j30 && adb install -r ${ANDROID_PRODUCT_OUT}/data/app/FrameworksCoreTests/FrameworksCoreTests.apk && adb shell am instrument -e class android.app.NotificationTest -w com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I0a8c95207ab42260d88e5c206a04ab8386376ac4