Add Campus EVPN-VXLAN fabric configs and host interfaces

- campus-spine1/2 (AS 66000): eBGP underlay + EVPN RR toward leafs
  and border leafs, addressing plan 10.1.x.x.
- campus-leaf1/2 (VTEP1, AS 66001, VTEP 10.1.255.11): VLAN 50
  (stretched L2 VXLAN, VNI 110050) and VLAN 60 (VRF gold anycast
  10.60.60.1, L3 VNI 100001).
- campus-leaf3/4 (VTEP2, AS 66002, VTEP 10.1.255.12): VLAN 50 and
  VLAN 70 (VRF gold anycast 10.60.70.1).
- border-leaf-campus1/2 (AS 66005, VTEP 10.1.255.21): MLAG pair,
  OSPF + eBGP to cores, VRF gold stitched via vxlan vrf gold
  vni 100001 with RT 1:100001.
- campus-access1/2: L2-only uplinks to campus leaf MLAG pairs,
  trunks VLAN 50+60 / 50+70.
- campus-host1/2 interface files: bond0 + VLAN sub-interfaces for
  the stretched L2 VLAN 50 and the VRF gold subnets.

hosts/campus-host1_interfaces

@@ -0,0 +1,26 @@
+auto lo
+iface lo inet loopback
+
+auto bond0
+iface bond0 inet manual
+    use bond
+    bond-slaves eth1 eth2
+    bond-mode 802.3ad
+    bond-miimon 100
+    bond-lacp-rate fast
+    up ip link set $IFACE up
+
+auto bond0.50
+iface bond0.50 inet static
+    address 10.50.50.101
+    netmask 255.255.255.0
+    vlan-raw-device bond0
+    up ip link set $IFACE up
+
+auto bond0.60
+iface bond0.60 inet static
+    address 10.60.60.101
+    netmask 255.255.255.0
+    gateway 10.60.60.1
+    vlan-raw-device bond0
+    up ip link set $IFACE up