Comment 1 for bug 1552506

In check-vlan-interface process, we should :
1. check server-A eth.vlan_id exists, A_exists = True/False
   1.1 if A_exists ==False, then add vlan interface in server-A
2. check server-B eth.vlan_id exists, B_exists = True/False
 2.1 if B_exists ==False, then add vlan interface in server-B

3. do some check else such as ping server-B form server-A via eth.vlan_id

4. teardown vlan_interface:
 4.1 if if A_exists ==False, then teardown vlan interface in server-A
 4.2 if if B_exists ==False, then teardown vlan interface in server-B

@bailin.zhang, do you agree with this?