Don't use /tmp for disk attach

[qiankehan]

Since qemu v5.2.0-rc0~110^2~1 util: give a specific error message when O_DIRECT doesn't work, it will report error when try to live attach file disk source from /tmp:

internal error: unable to execute QEMU command 'blockdev-add': Could not open '/tmp/disk-raw': filesystem does not support O_DIRECT

It seems some disk sources still use /tmp:

libvirt/tests/src/virsh_cmd/domain/virsh_detach_device.py:30:    def create_device_file(device_source="/tmp/attach.img"):

Here is why tmpfs cannot support O_DIRECT: https://lists.archive.carbon60.com/linux/kernel/720702

@chunfuwen @Yingshun @dzhengfy