Removing dependency on ONOS_ROOT in trellisp4.py

Change-Id: I9cb37de2487b9e4e97c730f16035fb6c82989e80
diff --git a/trellis/trellisp4.py b/trellis/trellisp4.py
index 6522bd0..1adae81 100755
--- a/trellis/trellisp4.py
+++ b/trellis/trellisp4.py
@@ -5,13 +5,6 @@
 import argparse
 sys.path.append('..')
 
-if 'ONOS_ROOT' not in os.environ:
-    print "Environment var $ONOS_ROOT not set"
-    exit()
-else:
-    ONOS_ROOT = os.environ["ONOS_ROOT"]
-    sys.path.append(ONOS_ROOT + "/tools/dev/mininet")
-
 from mininet.topo import Topo
 from mininet.net import Mininet
 from mininet.cli import CLI