ensure fragment start before synchronize to live edge

[jprorikon]

This PR will...

ensure fragment start before synchronize to live edge

Why is this Pull Request needed?

player synchronized to 0.00 with bad internet conditions. which live stream level list has short fragment and small length of fragments list.

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

Not have any other function change

Resolves issues:

#6685

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

[robwalch]

This is not an acceptable change. Re-syncing to the live edge is necessary in cases where media was never appended, but playlists were updated to the point that the current time or earlier sync/start time is no longer available.

[jprorikon]

thanks for your reply.
I would like to draw back the pr and reconsider how to deal with Re-syncing