fix: do not call load after mediachange for hls playlist loader

[dzianis-dashkevich]

Description

During ABR switch or fast quality switch, we call switchMedia_ which will call this.mainPlaylistLoader_.media with a new media. We request a new playlist and trigger a mediachange event right after the request.

In playlist controller we listen to the mediachange and call this.mainPlaylistLoader_.load()

in the load method, we hit the following check

if (media && !media.endList) {
  this.trigger('mediaupdatetimeout');
} else {
  this.trigger('loadedplaylist');
}

So for live, we trigger mediaupdatetimeout , which means that we need to refresh a live playlist, so we start loading the playlist a second time.

So we load the same playlist immediately (right after it was loaded), so we hit playlistunchanged flow.

Specific Changes proposed

This line was introduced mainly to fix dash-specific issues in this PR:
#1339

so the easiest solution is to call it for dash only.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (f294133) 86.16% compared to head (944c2c0) 86.15%.

Files	Patch %	Lines
src/playlist-controller.js	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1447      +/-   ##
==========================================
- Coverage   86.16%   86.15%   -0.01%     
==========================================
  Files          42       42              
  Lines       10613    10614       +1     
  Branches     2445     2446       +1     
==========================================
  Hits         9145     9145              
- Misses       1468     1469       +1     

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