PackageManager: Remove obsolete SCAN_NO_PATHS / SCAN_DEFER_DEX flags.

SCAN_NO_PATHS hasn't been used in the past several years, and was
introduced to deal with ASEC containers, and those are now handled by
DefaultContainerService.

SCAN_DEFER_DEX has been made obsolete by the JIT work we've done in N.

Test: make & boot
Change-Id: Ib2ffa8bd3c31d645a7efc5d78b03ca0774590f07