Add Remote ICMP support

Add remote ICMP support
This doesn't give me the accuracy I want:

Debug: 14:40:26.764549 info: put ping.rtt 1403293221 46 dst_host=ny-man02 host=grove

vs

Debug: 14:41:26.958222 info: put ping.rtt 1403293281 53.566572 dst_host=ny-man02 host=grove