Added Redfish login and logout for required test suites

Changes:
    - Added Redfish login and logout in suite setup and teardown
      of test_snmp_alerts_sub_menu.robot suite.
    - Added Redfish login and logout in test cases of
      test_network_sub_menu.robot and test_ldap_sub_menu.robot

Tested:
    - Ran successfully all test modified test cases from sandbox.

Change-Id: I51062feddd469ce2989c31289f34e9d38facfb91
Signed-off-by: Rahul Maheshwari <rahulmaheshwari@in.ibm.com>
diff --git a/gui/gui_test/settings_menu/test_snmp_alerts_sub_menu.robot b/gui/gui_test/settings_menu/test_snmp_alerts_sub_menu.robot
index 7d0c4ee..24cf8a5 100644
--- a/gui/gui_test/settings_menu/test_snmp_alerts_sub_menu.robot
+++ b/gui/gui_test/settings_menu/test_snmp_alerts_sub_menu.robot
@@ -9,7 +9,7 @@
 
 Suite Setup     Suite Setup Execution
 Suite Teardown  Close Browser
-
+Suite Teardown  Run Keywords  Redfish.Logout  AND  Close Browser
 
 *** Variables ***
 
@@ -243,6 +243,8 @@
     Click Element  ${xpath_snmp_alerts_sub_menu}
     Wait Until Keyword Succeeds  30 sec  10 sec  Location Should Contain  snmp-alerts
     Wait Until Element Is Not Visible   ${xpath_page_loading_progress_bar}  timeout=30
+    Redfish.Login
+
 
 Configure SNMP Manager Via GUI
     [Documentation]  Configure SNMP manager via GUI.