Make default 64-bit primary, 32-bit secondary

This is required to get aarch64 & x86_64 emulators booting
on lmp-preview-dev. Without this change, the system_server
is a 32 bit process but java only apps that use the
"android.uid.system" shared UID are dex2oated to 64 bit and
won't work correctly.

The correct fix needs build system changes, so this is the
easiest fix for now.

Note that this happens to work on volantis because the package
manager adjusts their ABI correctly during boot. That can't
happen on emulators because of dex-preopt; dex2oat can't oatify
a dex file from inside an existing oat file.

(cherry picked from commit d7950463)

Change-Id: Id94bcc382e90b279e726f2d1d0350fc60a5020df