ethernet: ARP disabled node

ethernet: ARP disabled node

Type: feature

improve the tracing from:

00:00:01:259665: pg-input
  stream pcap3, 42 bytes, 3 sw_if_index
  current data 0, length 42, buffer-pool 0, ref-count 1, trace handle 0x0
  ARP: 02:03:00:00:ff:02 -> ff:ff:ff:ff:ff:ff
  request, type ethernet/IP4, address size 6/4
  02:03:00:00:ff:02/172.16.3.5 -> 00:00:00:00:00:00/172.16.2.1
00:00:01:259690: ethernet-input
  frame: flags 0x1, hw-if-index 3, sw-if-index 3
  ARP: 02:03:00:00:ff:02 -> ff:ff:ff:ff:ff:ff
00:00:01:259702: arp-input
  request, type ethernet/IP4, address size 6/4
  02:03:00:00:ff:02/172.16.3.5 -> 00:00:00:00:00:00/172.16.2.1
00:00:01:259710: error-drop
  rx:pg2
00:00:01:259717: drop
  null-node: blackholed packets

to

00:00:01:283323: pg-input
  stream pcap3, 42 bytes, 3 sw_if_index
  current data 0, length 42, buffer-pool 0, ref-count 1, trace handle 0x0
  ARP: 02:03:00:00:ff:02 -> ff:ff:ff:ff:ff:ff
  request, type ethernet/IP4, address size 6/4
  02:03:00:00:ff:02/172.16.3.5 -> 00:00:00:00:00:00/172.16.2.1
00:00:01:283348: ethernet-input
  frame: flags 0x1, hw-if-index 3, sw-if-index 3
  ARP: 02:03:00:00:ff:02 -> ff:ff:ff:ff:ff:ff
00:00:01:283360: arp-input
  request, type ethernet/IP4, address size 6/4
  02:03:00:00:ff:02/172.16.3.5 -> 00:00:00:00:00:00/172.16.2.1
00:00:01:283369: arp-disabled
  request, type ethernet/IP4, address size 6/4
  02:03:00:00:ff:02/172.16.3.5 -> 00:00:00:00:00:00/172.16.2.1
00:00:01:283374: error-drop
  rx:pg2
00:00:01:283380: drop
  arp-disabled: ARP Disabled on this interface

Change-Id: I49b915b84cf56d6c138dedd8a596c045c150c4fb
Signed-off-by: Neale Ranns <nranns@cisco.com>