tests/vm: Do not use the -smp option with a single cpu

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20181013004034.6968-4-f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Fam Zheng <famz@redhat.com>

tests/vm/basevm.py

@@ -70,7 +70,7 @@ class BaseVM(object):
             "-device", "virtio-net-pci,netdev=vnet",
             "-vnc", "127.0.0.1:0,to=20",
             "-serial", "file:%s" % os.path.join(self._tmpdir, "serial.out")]
-        if vcpus:
+        if vcpus and vcpus > 1:
             self._args += ["-smp", str(vcpus)]
         if kvm_available():
             self._args += ["-enable-kvm"]