Added keyword Clean Up All Nodes to kill stale lxc processes in Suite Teardown

Change-Id: Iac5367cb5eb6158a1897ff05ff2fa1f77a6e3111
diff --git a/tests/functional/Voltha_MultiOLT_Tests.robot b/tests/functional/Voltha_MultiOLT_Tests.robot
index c92ba70..fbca7fe 100755
--- a/tests/functional/Voltha_MultiOLT_Tests.robot
+++ b/tests/functional/Voltha_MultiOLT_Tests.robot
@@ -191,3 +191,4 @@
 Teardown Suite
     [Documentation]    Clean up ONOS SSH connections
     Close All ONOS SSH Connections
+    Run Keyword If    ${has_dataplane}    Clean Up All Nodes