sdsWrite triggers a threshold event too often

[MiloradCvjetkovic]

sdsWrite triggers a threshold event SDS_EVENT_DATA_HIGH whenever there is already data over the threshold in the circular buffer.

Threshold event should only be triggered when an sdsWrite causes filling of the buffer to trigger level or beyond, and each further write, while there is more data in the buffer than threshold setting, should not trigger another threshold event.

This simplifies usage for the user as threshold event could be used for signaling that there is enough data for the algorithm to start processing, but no more threshold events would occur until new set of data is ready.