Allow to specify custom python path for TRex library

Change-Id: I380243038c53425355d1061b8a8ee38e0c7af407
diff --git a/TestON/tests/USECASE/SegmentRouting/QOS/QOS.topo b/TestON/tests/USECASE/SegmentRouting/QOS/QOS.topo
index 631d4e8..7aee367 100644
--- a/TestON/tests/USECASE/SegmentRouting/QOS/QOS.topo
+++ b/TestON/tests/USECASE/SegmentRouting/QOS/QOS.topo
@@ -37,6 +37,7 @@
                 <trex_config>trex_config.yaml</trex_config> <!-- relative path starting from ./dependencies-->
                 <force_restart>True</force_restart>
                 <software_mode>True</software_mode>
+                <trex_library_python_path>/home/jenkins/trex_python</trex_library_python_path>
             </COMPONENTS>
         </TRexClient>