add cbc-ping count and delay arguments

Currently, cbc-ping sends only one request. As such, it's unfortunately not very useful to see the app level ping time. The bootstrap node is consistently fast, but the other nodes are always slow because they need the bootstrap.

As an improvement, add count and delay arguments to cbc-ping so one can see those in the report.

I have no real input on arguments or output. It'd be nice if cbc-ping output remained the same, but adding a count greater than 1 would put it in a JSON array I guess. There might be other options for output too.