vxlan extended tests - fix scapy-related issues

- Add vxlan-gpe binding on udp port 4790 (taken from scapy upstream)
- VXLAN.VNI -> VXLAN.vni

Change-Id: If7ad38fa04fbfec01e01c81a06e88ffe70183672
Signed-off-by: Gabriel Ganne <gabriel.ganne@enea.com>

test/patches/scapy-2.3.3/vxlan.patch

@@ -0,0 +1,11 @@
+diff --git a/scapy/layers/vxlan.py b/scapy/layers/vxlan.py
+--- a/scapy/layers/vxlan.py
++++ b/scapy/layers/vxlan.py
+@@ -65,6 +65,7 @@
+             return self.sprintf("VXLAN (vni=%VXLAN.vni%)")
+
+ bind_layers(UDP, VXLAN, dport=4789)  # RFC standard port
++bind_layers(UDP, VXLAN, dport=4790)  # RFC standard vxlan-gpe port
+ bind_layers(UDP, VXLAN, dport=6633)  # New IANA assigned port for use with NSH
+ bind_layers(UDP, VXLAN, dport=8472)  # Linux implementation port
+ bind_layers(VXLAN, Ether, {'flags': 0x8})

test/test_vxlan_gpe.py

@@ -72,7 +72,7 @@ class TestVxlanGpe(BridgeDomain, VppTestCase):
         #  could be arbitrary.
         self.assertEqual(pkt[UDP].dport, type(self).dport)
         # Verify VNI
-        self.assertEqual(pkt[VXLAN].VNI, vni)
+        self.assertEqual(pkt[VXLAN].vni, vni)
 
     def test_decap(self):
         """ Decapsulation test