ONOS-7739 Support for P4Runtime multicast programming

Design doc: https://docs.google.com/document/d/13rkQlwr49M-uxQQEuxCMP7BFEPY2gtQ850Hn3gUfesU/edit#heading=h.lzdayib259sq

Change-Id: Ief00bec89fe5a9784b0ee13fdaafa3ae58ab654f
diff --git a/tools/dev/p4vm/bm-commands.sh b/tools/dev/p4vm/bm-commands.sh
index fdb8340..599f5c0 100644
--- a/tools/dev/p4vm/bm-commands.sh
+++ b/tools/dev/p4vm/bm-commands.sh
@@ -7,7 +7,7 @@
     fi
     tport=$(head -n 1 /tmp/bmv2-$1-thrift-port)
     echo "Starting CLI for BMv2 instance $1 (Thrift port $tport)..."
-    sudo bm_CLI --thrift-port ${tport} ${@:2}
+    sudo bm_CLI --thrift-port ${tport} --pre SimplePreLAG ${@:2}
 }
 
 bm-dbg () {