Restore terminal attributes for tty based monitor

Restore terminal attributes for tty based monitor

Patch http://permalink.gmane.org/gmane.comp.emulators.qemu/63472 handle
close when using tty devices (like /dev/ttyS0),
yet tty based monitor are not restoring terminal attributes (as done
with stdio based monitor), when closing qemu after that command:
$ qemu -monitor /dev/tty
the terminal is not responding until you write reset (blindly),
this patch fix it

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>