optimize nni-port handling

Change-Id: I957a4a40bbc8386c2b9dcd57837cba0af3549989
diff --git a/tests/functional/Voltha_MultiOLT_Tests.robot b/tests/functional/Voltha_MultiOLT_Tests.robot
index f16beb2..767b5f7 100755
--- a/tests/functional/Voltha_MultiOLT_Tests.robot
+++ b/tests/functional/Voltha_MultiOLT_Tests.robot
@@ -113,9 +113,7 @@
         ${of_id}=    Wait Until Keyword Succeeds    ${timeout}    15s    Validate OLT Device in ONOS
         ...    ${olt_serial_number}
         Set Global Variable    ${of_id}
-        ${nni_port}=    Run Keyword And Continue On Failure    Wait Until Keyword Succeeds    ${timeout}    2s
-        ...    Get NNI Port in ONOS    ${of_id}
-        Set Global Variable    ${nni_port}
+        ${nni_port}=    Wait Until Keyword Succeeds    ${timeout}    2s    Get NNI Port in ONOS    ${of_id}
         ${suppressaddsubscriber}=    Set Variable If    '${J}'=='0'    False    True
         Perform Sanity Test Per OLT    ${of_id}    ${nni_port}    ${olt_serial_number}   ${onu_count}
         ...    ${suppressaddsubscriber}
@@ -184,9 +182,7 @@
         ${of_id}=    Wait Until Keyword Succeeds    ${timeout}    15s    Validate OLT Device in ONOS
         ...    ${olt_serial_number}
         Set Global Variable    ${of_id}
-        ${nni_port}=    Run Keyword And Continue On Failure    Wait Until Keyword Succeeds    ${timeout}    2s
-        ...    Get NNI Port in ONOS    ${of_id}
-        Set Global Variable    ${nni_port}
+        ${nni_port}=    Wait Until Keyword Succeeds    ${timeout}    2s    Get NNI Port in ONOS    ${of_id}
         ${suppressaddsubscriber}=    Set Variable If    '${J}'=='0'    False    True
         Perform Sanity Test Per OLT    ${of_id}    ${nni_port}    ${olt_serial_number}   ${onu_count}
         ...    ${suppressaddsubscriber}