Modify IPv6 Test Case

Changes:
    - Added Teardown directive to clean up test exit

Tested:
    - Ran and Tested on BMC Environment.

Change-Id: I9c2f329105d67b209e3333e8dcc76dcfca6721bc
Signed-off-by: Vishal Kurkarni <kvishal@in.ibm.com>
diff --git a/redfish/managers/test_bmc_ipv6.robot b/redfish/managers/test_bmc_ipv6.robot
index 518628c..63a9aa0 100644
--- a/redfish/managers/test_bmc_ipv6.robot
+++ b/redfish/managers/test_bmc_ipv6.robot
@@ -84,6 +84,8 @@
 Modify IPv6 Address And Verify
     [Documentation]  Modify IPv6 address and verify.
     [Tags]  Modify_IPv6_Address_And_Verify
+    [Teardown]  Run Keywords
+    ... Delete IPv6 Address  ${test_ipv6_addr1}  AND  Test Teardown Execution
 
     Configure IPv6 Address On BMC  ${test_ipv6_addr}  ${test_prefix_length}