Removed import of KernelSwitch in toplogy files

Change-Id: I141c41e590a224be8c217602225c9d20a7b43516
diff --git a/TestON/tests/CHOtest/Dependencies/topoChordal.py b/TestON/tests/CHOtest/Dependencies/topoChordal.py
index 38eb6a1..542c3ed 100755
--- a/TestON/tests/CHOtest/Dependencies/topoChordal.py
+++ b/TestON/tests/CHOtest/Dependencies/topoChordal.py
@@ -10,7 +10,7 @@
 from mininet.cli import CLI
 from mininet.log import setLogLevel
 from mininet.util import dumpNodeConnections
-from mininet.node import ( UserSwitch, OVSSwitch, OVSLegacyKernelSwitch, IVSSwitch )
+from mininet.node import ( UserSwitch, OVSSwitch, IVSSwitch )
 
 class chordalTopo( Topo ):