Adjust forced dexopt in case of stripped APKs.

We cannot compile from scratch for strip APK. So
if getDexOptNeeded returns NotNeeded, pretend there was
a compiler filter change, in order to pick up the vdex file.

bug: 37558732
Test: "adb shell cmd package compile" of a stripped /system apk

(cherry picked from commit 96d12a93)

Change-Id: I3b699a18799ea035ff78c60578c08f8803a17e36