Forget about staged installs that are old or in a terminal state.

Bug: 122677682
Test: Install apex, reboot, reboot again. Inspect
data/system/install_sessions.xml in each instance to see that the
session is removed once the apex has been successfully applied.

Change-Id: I0a4009520f67e2a9fc1a6c2040c0dc89d2a7c13a