GUI: Updated CLI Get BMC DateTime and Modify BMC Date keywords

Changes:
    - Modified keyword called as CLI Get BMC DateTime.
    - Modified keyword called as Modify BMC Date .

Tested:
    - Successfully ran
      redfish/managers/test_certificate.robot

Change-Id: I1341b3670bd5ae6d496d06ea0e32e43091e7c62e
Signed-off-by: rramyasr-in <rramyasr@in.ibm.com>
diff --git a/redfish/managers/test_certificate.robot b/redfish/managers/test_certificate.robot
index db064ec..7d00362 100644
--- a/redfish/managers/test_certificate.robot
+++ b/redfish/managers/test_certificate.robot
@@ -264,7 +264,7 @@
     [Documentation]  Restore BMC date to its prior value.
 
     Redfish.Patch  ${REDFISH_BASE_URI}Managers/${MANAGER_ID}  body={'DateTime': '${cli_date_time}'}
-    ...  valid_status_codes=[${HTTP_OK}]
+    ...  valid_status_codes=[${HTTP_OK}, ${HTTP_NO_CONTENT}]
 
 
 Generate CSR Via Redfish