GUI: Added Redfish Login and Logout in the test suite

Change:
     - Added Redfish.Login and added Redfish.Logout in the test case

Tested:
    - Ran successfully test_certificates_sub_menu.robot

Change-Id: I78da22fb6765e5fb4d5012878488256ec490c6a4
Signed-off-by: rramyasr-in <rramyasr@in.ibm.com>
diff --git a/gui/gui_test/security_and_access_menu/test_certificates_sub_menu.robot b/gui/gui_test/security_and_access_menu/test_certificates_sub_menu.robot
index 6c15780..e39ca18 100644
--- a/gui/gui_test/security_and_access_menu/test_certificates_sub_menu.robot
+++ b/gui/gui_test/security_and_access_menu/test_certificates_sub_menu.robot
@@ -97,7 +97,9 @@
     [Tags]  Verify_Installed_HTTPS_Certificate
 
     # Replace HTTPS certificate.
+    Redfish.Login
     Replace Certificate Via Redfish  Server   Valid Certificate Valid Privatekey  ok
+    Redfish.Logout
 
     # Verify certificate is available in GUI.
     Wait Until Page Contains  HTTPS Certificate  timeout=10