bpf dumper: Implement command line tool felix-xdp for debugging XDP maps
bpf dumper: Implement command line tool felix-xdp for debugging XDP maps

It can dump the content of the failsafe port map and the blacklist map
for all network interfaces with a XDP program attached.

$ sudo -E go run bpf/cmd/felix-xdp.go dump
Failsafe ports:
  TCP: 22
  UDP: 53
  TCP: 53
  TCP: 80
Interfaces with blacklist:
  eth42:
    1.1.0.0/16 value=1
    8.8.0.0/16 value=1

Additionally, for debugging, maps can be populated with example values
by the "populate" command:

$ sudo -E go run bpf/cmd/felix-xdp.go populate

neiljerram/felix,Metaswitch/calico,neiljerram/felix,Metaswitch/calico,neiljerram/felix,neiljerram/felix