PackageManager: allow forcing pre-dexopt on eng builds

prop: debug.dalvik.force.dexopt=true

Change-Id: I2bdfaa307572b9bd6b2bebc35c18dc30974aa024
Handle nested folder case

Change-Id: Id6d6a5899e8255d18192adbc766d8d9a0e6825d0
Signed-off-by: Roger Chen <cxr514033970@gmail.com>
Merge "PackageManager: allow forcing pre-dexopt on eng builds" into jellybean
Merge remote-tracking branch 'github/jellybean' into aosp