ping: allow the user to send bursts of N packets instead of single packet
ping: allow the user to send bursts of N packets instead of single packet

Change-Id: I3c1d3a2db56487473123e6fec2b076a063473313
Signed-off-by: Andrew Yourtchenko <eb6233fe2fbd585844f4fb8426b53b186ab379b1@gmail.com>

chrisy/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,vpp-dev/vpp,vpp-dev/vpp,FDio/vpp,milanlenco/vpp,milanlenco/vpp,milanlenco/vpp,chrisy/vpp,milanlenco/vpp,vpp-dev/vpp,chrisy/vpp,chrisy/vpp,vpp-dev/vpp,FDio/vpp,vpp-dev/vpp,FDio/vpp,FDio/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,vpp-dev/vpp,milanlenco/vpp,chrisy/vpp,milanlenco/vpp,chrisy/vpp