Unsynchronized audio after progressing to the next lesson

[dachev]

Issue Title

Audio and video become unsynchronized after progressing to the next lesson if the playback rate is > 1. This happens when streaming remote content but NOT when playing locally downloaded lessons.

Issue Description

Steps to Reproduce

The most import part.

1. Play a lesson at 2x
2. Wait for lesson the end and start playing the next one

Actual and Expected Result

Expected:
Playback as usual

Actual:
Audio and video may go unsynchronized