Enable and Refactor Failing Manifest Retry Tests
Enable and Refactor Failing Manifest Retry Tests

We have tests that check that we can interrupt manifest fetching
(network retries). These were disabled because they did not play
nicely with the load graph's atomic step model.

This change re-enables the tests (even through they will fail) and
updates them to use ES6.

Issue #1157

Change-Id: Id4e2f177db88aae3b7c2da15f11457a6715cc309

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