[VOL-4494] Added keyword Clean Up All Nodes to kill stale lxc processes in Suite Teardown

Change-Id: I44f0d1a070f9db8f8b8e88b0c4dafa141aabdd7c
diff --git a/tests/functional/Voltha_MultiOLT_Tests.robot b/tests/functional/Voltha_MultiOLT_Tests.robot
index 767b5f7..0a97bc2 100755
--- a/tests/functional/Voltha_MultiOLT_Tests.robot
+++ b/tests/functional/Voltha_MultiOLT_Tests.robot
@@ -211,3 +211,4 @@
 Teardown Suite
     [Documentation]    Clean up ONOS SSH connections
     Close All ONOS SSH Connections
+    Run Keyword If    ${has_dataplane}    Clean Up All Nodes