Solve potential race condition on known_hosts file when executing
scripts in parallel

Change-Id: I4b1eb76a79d978a9241cd08df49d9ed87e90cdc3
diff --git a/tools/test/bin/onos b/tools/test/bin/onos
index 44ba393..c74ebc6 100755
--- a/tools/test/bin/onos
+++ b/tools/test/bin/onos
@@ -34,4 +34,4 @@
 
 [ -n "$1" ] && OCI=$(find_node $1) && shift
 
-ssh -p 8101 -o StrictHostKeyChecking=no $OCI "$@"
+ssh -q -p 8101 -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null $OCI "$@"