Added new testcase to VMI menu

Changes:
    - Added "Enable VMI DHCPv6 On Eth0 While Eth1
      Has DHCPv6 And Verify" testcase
    - Added "Enable VMI DHCPv6 On Eth1 While Eth0
      Has DHCPv6 And Verify" testcase

Tested :
    - Ran and Tested on BMC Environment

Change-Id: I886e264929c4986a168b5df3326b5958c0550758
Signed-off-by: Megha G N <Megha.G.N@ibm.com>
diff --git a/lib/external_intf/vmi_utils.robot b/lib/external_intf/vmi_utils.robot
index 03a504d..b313b6f 100644
--- a/lib/external_intf/vmi_utils.robot
+++ b/lib/external_intf/vmi_utils.robot
@@ -267,8 +267,8 @@
 
 Set VMI DHCPv6 Property
     [Documentation]  Set VMI DHCPv6 attribute.
-    [Arguments]  ${dhcpv6_operatingmode}=${Disabled}  ${valid_status_code}=${HTTP_ACCEPTED}
-    ...  ${interface}=${ethernet_interface}
+    [Arguments]  ${dhcpv6_operatingmode}=${Disabled}
+    ...  ${interface}=${ethernet_interface}  ${valid_status_code}=${HTTP_ACCEPTED}
 
     # Description of argument(s):
     # dhcpv6_operatingmode    Enabled if user wants to enable DHCPv6.