Fixed bug with PDU handling in headless mode

[robeving]

This fixes a bug with headless replay of files, specifically those created by pyrdp-convert.py which seems to set the timestamp to 0. Using the timestamp is probably bad anyway due to the risk of collision.

[robeving]

Fixes https://github.com/GoSecure/pyrdp/issues/445

[obilodeau]

This fix artificially accelerates all replays when played in pyrdp-player.py because it squeezes all events together leaving no silence between events. It cannot be merged like that.