TESTS: Add tests for fix of end-time functionality in the video player

**Description**

Just tests need to be written for cases when there is an-end time.

#### 1.)

    Whenever the video is playing, and the point of end-time is reached, the video pauses.
    If the user then clicks play while the scroll bar is located at end-time, the video continues playing from end-time to the end.

#### 2.)

    Given a video with end-time at 1:00
    when the video starts playing from :50
    Then the video will stop playing at 1:00

#### 3.)

    Given a video with end-time at 1:00 and start-time at :30
    when the video starts playing from :15
    Then the video will stop playing at 1:00

#### 4.)

    Given a video with end-time at 1:00
    when the video starts playing at 1:10
    Then the video stops playing at the end of the video

#### 5.)

    Given a video with end-time at 1:00
    when the video starts playing at 1:00
    Then the video plays
    and the video stops playing at the end of the video.

**Jira issue**

[BLD-662](https://edx-wiki.atlassian.net/browse/BLD-662)

**Reviewers**

- @polesye