Allow to read all params used to create session.

So that they can be verified by the app calling commit().

This really only makes sense if the app calling commit is different from
the app that created the session.

Bug: 37281396
Test: cts-tradefed run cts-dev -m CtsContentTestCases --test=android.content.pm.cts.InstallSessionTransferTest
      Installed and uninstalled packages via the PackageInstaller app

Change-Id: I5c954ca59b7582555bea847f3ddbba0aeefba301