Auto increment Local UDP Port for new RTP stream

[mikebotts]

By default, connecting two Garmin Virbs to an OSH instance causes a conflict between the video streams ... only the last connected gets the video stream. This is because both sensors use the same RTP/RTPS Local UDP Port.

This can be fixed by manually assigning a different Port for each sensors in the Admin panel, but would be better handled by OSH automatically detect this conflict and increment the Port number by one when a new RTP source is being added.