Bring install and install-multiple into parity.

This ensures that both are using (almost) identical logic when
deciding what installs to proceed with.  Installs from "pm" for all
users now run as OWNER, and rely solely on INSTALL_ALL_USERS to
express intent.  This keeps install session notifications simple.

Since installer UID can vary from installer package name, start
persisting the UID.  Also parse some missing flags for install
sessions.

Bug: 17469392
Change-Id: I6d89b1a787aa2024cc4bebf6b9c29317c358e147