Remove redfish login and logout from lib code

With this change, the test script caller is expected to have the
valid session before invoking the changed keywords in library.

Changes:
      - Remove login/logout from lib/bmc_redfish_utils.robot
        for power and reset operation.
      - Update impacted test suites.

Tested: To identify the impact, ran the existing test bucket and
        the result is looking good.

Change-Id: I6df69d6fcc4c38470fdb2ec3b31fb28beb726d70
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/redfish/account_service/test_user_account.robot b/redfish/account_service/test_user_account.robot
index 00e19c0..e3b3d2a 100644
--- a/redfish/account_service/test_user_account.robot
+++ b/redfish/account_service/test_user_account.robot
@@ -5,6 +5,7 @@
 Resource         ../../lib/bmc_redfish_resource.robot
 Resource         ../../lib/openbmc_ffdc.robot
 
+Suite Setup      Suite Setup Execution
 Test Setup       Test Setup Execution
 Test Teardown    Test Teardown Execution
 
@@ -33,7 +34,6 @@
 
     # Reboot BMC.
     Redfish OBMC Reboot (off)  stack_mode=normal
-    Redfish.Login
 
     # Verify users after reboot.
     Redfish Verify User  admin_user     TestPwd123  Administrator   ${True}
@@ -487,3 +487,9 @@
 
     # Delete newly created user.
     Redfish.Delete  /redfish/v1/AccountService/Accounts/${username}
+
+
+Suite Setup Execution
+    [Documentation]  Do test case setup tasks.
+
+    Redfish.Login