Allow overwriting test's report stdout text from inside test code

Change-Id: Ie1c0ecf7464209a4241665025fda33ae624fc049
diff --git a/suites/4g/iperf3_dl.py b/suites/4g/iperf3_dl.py
index fd77cd3..c98251b 100755
--- a/suites/4g/iperf3_dl.py
+++ b/suites/4g/iperf3_dl.py
@@ -45,4 +45,5 @@
 
 max_rate = enb.ue_max_rate(downlink=True)
 res_str = ue.verify_metric(max_rate * 0.9, operation='avg', metric='dl_brate', criterion='gt')
-print(res_str + '\n')
+print(res_str)
+test.set_report_stdout(res_str)