iperf3: macOS server compatibility

Result message does not appear to encode start, end time, so work around,
using the t3, t0 timestamps used else where for sending.

Fixes #665

Author: graeme-winter

python-ecosys/iperf3/iperf3.py

@@ -147,10 +147,10 @@ def stop(self):
 
     def report_receiver(self, stats):
         st = stats["streams"][0]
-        dt = st["end_time"] - st["start_time"]
+        dt = ticks_diff(self.t3, self.t0)
         self.print_line(
-            st["start_time"],
-            st["end_time"],
+            st.get("start_time", 0.0),
+            st.get("end_time", dt * 1e-6),
             st["bytes"],
             st["packets"],
             st["errors"],