fix flannel's cross vm networking for vagrant

* set flannel backend type to `host-gw`
* set flannel interface to be eth1 ip

roles/network_plugin/flannel/tasks/main.yml

@@ -4,6 +4,7 @@
     src: network.json
     dest: /etc/flannel-network.json
     backup: yes
+
 - name: Flannel | Create flannel pod manifest
   template:
     src: flannel-pod.yml