NMS-6689: Documentation StrafePingMonitor

to the best of my knowledge
StrafePing is a special case because it returns more than just the response time.

Typically, all the monitors return the response time in milliseconds (except the IcmpMonitor that returns the response time in microseconds).

StrafePing (and I believe there are others), returns the following:

- pingN (the response time for each ping, N indicates each attempt).
- loss
- median
- respose-time