netperf: fix wrong IP in netperf cmdline

commit [1] introduced a regression, it wrongly update the server_ip
to ip address of control connection.

We have two nics, the first (virtio-net) is data connection, the second
nic (non virtio-net) is control connection.

[1] https://github.com/kongove/virt-test/commit/63ada005Signed-off-by: NAmos Kong <akong@redhat.com>

generic/tests/netperf.py

@@ -140,7 +140,7 @@ def run(test, params, env):
 
     if len(params.get("nics", "").split()) > 1:
         vm.wait_for_login(nic_index=1, timeout=login_timeout)
-        server_ip = vm.wait_for_get_address(1, timeout=5)
+        server_ctl_ip = vm.wait_for_get_address(1, timeout=5)
 
     logging.debug(commands.getoutput("numactl --hardware"))
     logging.debug(commands.getoutput("numactl --show"))