Correct ordering of Build ONU SN List parameters

Change-Id: I96c7d585a33bf91436adb50eb64fec63d3d27f8b
diff --git a/tests/dt-workflow/Voltha_DT_PODTests.robot b/tests/dt-workflow/Voltha_DT_PODTests.robot
index 36ff38b..94b7fac 100644
--- a/tests/dt-workflow/Voltha_DT_PODTests.robot
+++ b/tests/dt-workflow/Voltha_DT_PODTests.robot
@@ -268,7 +268,7 @@
         ...    ${olt_device_id}
         ${List_ONU_Serial}    Create List
         Set Suite Variable    ${List_ONU_Serial}
-        Build ONU SN List    ${List_ONU_Serial}    ${num_onus}    ${olt_serial_number}
+        Build ONU SN List    ${List_ONU_Serial}    ${olt_serial_number}    ${num_onus}
         Log    ${List_ONU_Serial}
         Run Keyword    Wait Until Keyword Succeeds    ${timeout}    5s    Validate ONU Flows
         ...    ${List_ONU_Serial}    ${onu_flows}