Fix multiArch parsing for ApkLite.

Two separate issues :
- We were not parcelling the value at all.
- We were looking for it in the wrong manifest attribute.

Note that this change has no observable effect on installs (which
is probably why it wasn't caught so far). This code path is only
used in FileInstallArgs.copyApk (where multiArch was effectively
false before this change) but the package manager extracts shared
libs *again* inside scanPackageLI where this was being done
correctly since the value there came from a "full" package
parse, and not a "lite" package parse.

Change-Id: I54c3efcf8f57e6970f8fbde8cd1f57d487b13114