Fix DRM test errors on IE and Edge
Fix DRM test errors on IE and Edge

Somehow, errors thrown by CastReceiver unit test setup caused DRM
tests on IE and Edge to fail.  This cleans up the Cast tests to fix
these uncaught errors that somehow polluted the DRM tests.

Change-Id: I435ff994b0b70199eb5a8febd419296b59497920

TheModMaker/shaka-player,indiereign/shaka-player,vimond/shaka-player,tvoli/shaka-player,tvoli/shaka-player,tvoli/shaka-player,indiereign/shaka-player,vimond/shaka-player,vimond/shaka-player,shaka-project/shaka-player,indiereign/shaka-player,TheModMaker/shaka-player,tvoli/shaka-player,TheModMaker/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,TheModMaker/shaka-player,shaka-project/shaka-player