Remove fragment from fragment tracker on BUFFER_FULL error and when i…

[robwalch]

This PR will...

Remove fragment from fragment tracker:

1. on BUFFER_FULL error
2. when fragment is tracked at APPENDING but (audio) stream controller is trying to reload in IDLE state (fragment loading or append was aborted)

Why is this Pull Request needed?

Stream controllers will not reload segments in APPENDING state, however if the controller is trying to load a segment, then it should have exited the parsing and append cycle. Whenever this happens the fragment(s) should be removed from the tracker so that they can be reloaded.

Are there any points in the code the reviewer needs to double check?

Resolves issues:

Resolves #5328
Related to #5349 / Follow up to #5350

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md