Enable constant lag for JIT HLS

If you observe that the HDS fragments arrive out-of-order at the origin server, set //Config/FaultTolerance/ConstantLagFromLiveEdge in the stream.xml file to the maximum amount of time (in seconds) for which a fragment can fall out-of-order. This causes the live edge of the just-in-time HLS stream to lag behind the live edge of the source HDS by the configured time. This should resolve any problem in just-in-time HLS due to out-of-order fragment pushes.