Disable http range requests in pdf.js.

A bug in pdf.js or Chrome is causing pdf books to not load.

TNL-488
Disabled failing test test_video_end_time_with_default_start_time.
Merge pull request #5455 from edx/usman/tnl488-disable-range-requests-in-pdf-viewer

Disable range requests in pdf viewer.
Merge pull request #5461 from edx/release

Release