Video: Fix issues related to videos that have separate YouTube IDs for the different video speeds.

Tickets: [BLD-915](https://edx-wiki.atlassian.net/browse/BLD-915), [BLD-901](https://edx-wiki.atlassian.net/browse/BLD-901) .

**Steps to reproduce:**
Youtube html5
1. Create youtube video with `youtube_id_1_5` field that has transcript file for this speed.
2. Select 1.5x video speed.
3. Reload the page 
4. See the transcript are loaded for `youtube_id_1_5`, but must be for `youtube_id_1_0`. The same situation with video duration. 

@auraz , @valera-rozuvan please review.