Revert "vold: Allow ASEC containers on an external volume when internal is emulated"

This reverts commit ee7a7d2eced70910f7cdb335936e0f116ed6d53a.
Revert "Revert "vold: Allow ASEC containers on an external volume when internal is emulated""

This reverts commit 70e4dc5bb1b9371af57161c9ba114a816960c183.