Block new installs into ASEC containers.

ASEC containers have been deprecated since MNC, which is when we
introduced the "adoptable storage" feature.  Adoptable storage is a
much better user experience, since we move both the APK and private
app data together as a single unit, making it much easier to explain
to users.

Test: builds, boots
Bug: 32913676
Change-Id: I97385d081a50a79fc005d4e23e09999f9ae6cfc1