Collector to report median instead of average ping.

**Description**

The collector currently reports average ping for the node. This has often led to skewed display of the node's connectivity since if one node has high latency, and the other 6 very low, the average will still be high.

I think the time is long overdue to instead report the median for this particular value.

In order to ease transition on the network dashboard we should probably retain the average value as well.