Add delay before recording archiving to workaround Red5 race

Right now there is a possibility that the rap-worker process might
see the recording.done file (written by bbb-web) prior to Red5 having
completed writing the video files to disk.

This happens most often when a meeting end api request is sent while a
webcam is visible.

Add a delay (currently 2 minutes) before the archive scripts are run
to work around the issue. Real fix is far more complicated...