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

Change-Id: Iac5367cb5eb6158a1897ff05ff2fa1f77a6e3111
diff --git a/tests/functional/Voltha_FailureScenarios.robot b/tests/functional/Voltha_FailureScenarios.robot
index e0e8eb7..add8f1b 100755
--- a/tests/functional/Voltha_FailureScenarios.robot
+++ b/tests/functional/Voltha_FailureScenarios.robot
@@ -805,3 +805,4 @@
 Teardown Suite
     [Documentation]    Clean up ONOS SSH connections
     Close All ONOS SSH Connections
+    Run Keyword If    ${has_dataplane}    Clean Up All Nodes