tools/selftests: Use a sensible timeout value for iperf3 client

The default timeout of cmd() is 5 seconds and Iperf3Runner requests the
iperf3 client to run for 10 seconds, which clearly doesn't work since
commit [1] enforced the timeout parameter.

Use a value derived from duration as timeout (+5 seconds for
startup/teardown/various other overhead).

[1] commit f0bd193166 ("selftests: net: fix timeout passed as positional argument to communicate()")
Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

tools/testing/selftests/drivers/net/lib/py/load.py

@@ -48,7 +48,10 @@ class Iperf3Runner:
         Starts the iperf3 client with the configured options.
         """
         cmdline = self._build_client(streams, duration, reverse)
-        return cmd(cmdline, background=background, host=self.env.remote)
+        kwargs = {"background": background, "host": self.env.remote}
+        if not background:
+            kwargs["timeout"] = duration + 5
+        return cmd(cmdline, **kwargs)
 
     def measure_bandwidth(self, reverse=False):
         """