Move from dalvik.vm.image-dex2oat-flags to dalvik.vm.dex2oat-filter [build]

This will allow us to conditionally change the compiler-filter based on other properties.

Bug: 15165413

(cherry picked from commit 4d30e5e2)

Change-Id: I84e8038c6536291e6775f39b33556b8169fdf292