Allow events from expired EME sessions.
Allow events from expired EME sessions.

When we close an expired EME session, we can still get a key status
changed event.  This fixed an assertion failure caused by this.

Fixes #1599

Change-Id: I49fd02151f8907c3868080e5c5dcd912fd25ecd4

tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,tvoli/shaka-player