Fix bug when deleting expired EME sessions.
Fix bug when deleting expired EME sessions.

Normally we close sessions that are expired to clean up old sessions.
However, we shouldn't do this while deleting offline sessions since
it will orphan the session and take up resources.

This also fixes a bug where deleting content that has expired sessions
will hang forever.

Change-Id: I1b7384dba2b282ebeb7f9c12e2665797940f97f5

tvoli/shaka-player,indiereign/shaka-player,Ross-cz/shaka-player,TheModMaker/shaka-player,vimond/shaka-player,TheModMaker/shaka-player,brightcove/shaka-player,brightcove/shaka-player,russitto/shaka-player,TheModMaker/shaka-player,vimond/shaka-player,indiereign/shaka-player,indiereign/shaka-player,Ross-cz/shaka-player,vimond/shaka-player,shaka-project/shaka-player,russitto/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,russitto/shaka-player,Ross-cz/shaka-player,shaka-project/shaka-player,TheModMaker/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,brightcove/shaka-player,tvoli/shaka-player