iperf3: Support configuring data direction (dl vs ul)

Change-Id: I6b5b740beac22015c952ce826c034031ad4c4465
diff --git a/suites/4g/iperf3.py b/suites/4g/iperf3.py
index 5ccc922..cc7bca0 100755
--- a/suites/4g/iperf3.py
+++ b/suites/4g/iperf3.py
@@ -32,7 +32,7 @@
 ue.connect(enb)
 
 iperf3srv.start()
-proc = iperf3cli.prepare_test_proc(ue.netns())
+proc = iperf3cli.prepare_test_proc(False, ue.netns())
 
 print('waiting for UE to attach...')
 wait(ue.is_connected, None)