VM: Use -serial none in no-graphics kvm mode...

lib/cros_vm_lib.sh

 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # Common vm functions for use in crosutils.
 
 DEFINE_string kvm_pid "" \
   "Use this pid file.  If it exists and is set, use the vm specified by pid."
 DEFINE_boolean no_graphics ${FLAGS_FALSE} "Runs the KVM instance silently."
 DEFINE_boolean persist "${FLAGS_FALSE}" "Persist vm."
@@ skipping 22 matching lines @@
       # Let's be safe in case they specified a file that isn't a pid file.
       echo "File ${KVM_PID_FILE} exists but specified pid doesn't." >&2
       exit 1
     fi
   else
     # No pid specified by PID file.  Let's create a VM instance in this case.
     echo "Starting a KVM instance" >&2
     local nographics=""
     local usesnapshot=""
     if [ ${FLAGS_no_graphics} -eq ${FLAGS_TRUE} ]; then
-      nographics="-nographic"
+      nographics="-nographic -serial none"
     fi
 
     if [ ${FLAGS_snapshot} -eq ${FLAGS_TRUE} ]; then
       snapshot="-snapshot"
     fi
 
     sudo kvm -m 1024 \
       -vga std \
       -pidfile "${KVM_PID_FILE}" \
       -daemonize \
@@ skipping 41 matching lines @@
     if [ -n "${pid}" ]; then
       echo "Killing ${pid}" >&2
       sudo kill ${pid}
       sudo rm "${KVM_PID_FILE}"
     else
       echo "No kvm pid found to stop." >&2
       return 1
     fi
   fi
 }