Fragment + Playlist loaders are not always destroyed before freeing

[mfedderly]

What version of Hls.js are you using?

0.11.0

What browser and OS are you using?

Chrome

Checklist

• The issue observed is not already reported by searching on Github under https://github.com/video-dev/hls.js/issues
• The issue occurs in the stable client on https://hls-js.netlify.com/demo and not just on my page

• The issue occurs in the latest client on https://hls-js-latest.netlify.com/demo and not just on my page

• The stream has correct Access-Control-Allow-Origin headers (CORS)
• There are no network errors such as 404s in the browser console when trying to play the stream

Steps to reproduce

1. Implement a custom loader that has resources that must be freed when the loader is no longer in use
2. Notice that the fragment and playlist loaders are created but not destroyed due to memory leak

Expected behavior

Before freeing a loader instance, the destroy method is called

Actual behavior

The loader is freed without calling destroy first

[itsjamie]

Link #2123.