pkt-gen: Bug fix on pinger-body.
pkt-gen: Bug fix on pinger-body.

This patch fixes a bug that pinger-body embeds 16-byte
struct timespec into a 14 byte payload space (after 4 byte
sequence number)

luigirizzo/netmap,luigirizzo/netmap,luigirizzo/netmap,luigirizzo/netmap,luigirizzo/netmap