Fix to allow self-updates without user action.

Check if the *current* installer package (ie. the session owner) is
allowed to install packages when deciding if user action is needed. We
were mistakenly checking the *existing* installer package (ie. installer
of record) instead, which prevented self-updates.

Bug: 184741940
Test: Manual with local test app.
Change-Id: Ie0aec7a34ead94788af462002d6dccf420f9f50b