Fix neighbor discovering

[glazychev-art]

Motivation

Cilium CNI plugin uses /32 for hosts addresses.
When we inject the host interface to VPP, we try to resolve the gateway MAC using ARP Request. But when we receive the ARP reply, VPP cannot handle it, because:

00:03:50:190782: af-packet-input
  af_packet: hw_if_index 1 rx-queue 0 next-index 4
    tpacket2_hdr:
      status 0x1 len 42 snaplen 42 mac 66 net 80
      sec 0x6565ca18 nsec 0xc19ad4 vlan 0 vlan_tpid 0
    vnet-hdr:
      flags 0x00 gso_type 0x00 hdr_len 0
      gso_size 0 csum_start 0 csum_offset 0
00:03:50:190793: ethernet-input
  ARP: 22:88:cd:e1:98:ba -> 82:9f:51:46:12:92
00:03:50:190800: arp-input
  reply, type ethernet/IP4, address size 6/4
  22:88:cd:e1:98:ba/10.244.2.250 -> 82:9f:51:46:12:92/10.244.2.154
00:03:50:190803: arp-reply
  reply, type ethernet/IP4, address size 6/4
  22:88:cd:e1:98:ba/10.244.2.250 -> 82:9f:51:46:12:92/10.244.2.154
00:03:50:190812: error-drop
  rx:host-eth0
00:03:50:190813: drop
  arp-reply: IP4 source address not local to subnet

Solution:
Resolve the gateway MAC address before we inject the AF_PACKET host interface to VPP

Issue:
networkservicemesh/deployments-k8s#10581