Fix iperf test and make server/client jobs to write to different result log directory.

server/tests/iperf/iperf.py

 from autotest_lib.server import autotest, hosts, subcommand, test
 from autotest_lib.server import utils
 
 class iperf(test.test):
     version = 1
 
     def run_once(self, pair, udp, bidirectional, time, stream_list):
         print "running on %s and %s\n" % (pair[0], pair[1])
 
         # Designate a lable for the server side tests.
@@ skipping 22 matching lines @@
                             "test_time=%d, stream_list=%s, tag='%s')"])
 
         server_control_file = template % (server.ip, client.ip, 'server', udp,
                                           bidirectional, time, stream_list,
                                           tagname)
         client_control_file = template % (server.ip, client.ip, 'client', udp,
                                           bidirectional, time, stream_list,
                                           tagname)
 
         server_command = subcommand.subcommand(server_at.run,
-                         [server_control_file, server.hostname])
+                         [server_control_file, server.hostname],
+                         subdir='server')
         client_command = subcommand.subcommand(client_at.run,
-                         [client_control_file, client.hostname])
+                         [client_control_file, client.hostname],
+                         subdir='client')
 
         subcommand.parallel([server_command, client_command])
 
         for m in [client, server]:
             status = m.run('iptables -L')
             if not status.exit_status:
                 m.enable_ipfilters()