Fix potential divide by zero. Increased latency parameters to threshold=0.50,...

Fix potential divide by zero. Increased latency parameters to threshold=0.50, history=10. Maybe it's just because my control plane is over a VPN and over the public internet, but the link latencies are fluctuating a bit. TODO evaluate whether or not we should completely clear the average/history each time we accept a new latency value. This would lessen the number of latency updates.