Changing the way VOLTCONFIG is passed to voltctl, required to support dynamic changes of the config for multi-stack setups

Change-Id: I23ab2500255c35207df9c368d2656e502337dff2
diff --git a/tests/functional/Voltha_multipleOLTTests.robot b/tests/functional/Voltha_multipleOLTTests.robot
index 7161d6d..831afc1 100755
--- a/tests/functional/Voltha_multipleOLTTests.robot
+++ b/tests/functional/Voltha_multipleOLTTests.robot
@@ -67,7 +67,7 @@
 Setup Suite
     [Documentation]    Setup the test suite
     Set Global Variable    ${KUBECTL_CONFIG}    export KUBECONFIG=%{KUBECONFIG}
-    Set Global Variable    ${VOLTCTL_CONFIG}    export VOLTCONFIG=%{VOLTCONFIG}
+    Set Global Variable    ${VOLTCTL_CONFIG}    %{VOLTCONFIG}
     ${k8s_node_ip}=    Evaluate    ${nodes}[0].get("ip")
     ${ONOS_REST_IP}=    Get Environment Variable    ONOS_REST_IP    ${k8s_node_ip}
     ${ONOS_SSH_IP}=     Get Environment Variable    ONOS_SSH_IP     ${k8s_node_ip}