virt-install is not part of libvirt. It is part of a separate tool, virtinst. It looks like this command is setting the "<on_poweroff>destroy</on_poweroff>" that you don't want.
I suggest that you read the virt-install documentation carefully, and if this still doesn't explain its behaviour and you think there's a bug in virt-install that incorrectly sets this flag, then to explain the details reassign this bug to "virtinst" and mark it as New.
virt-install is not part of libvirt. It is part of a separate tool, virtinst. It looks like this command is setting the "<on_poweroff> destroy< /on_poweroff> " that you don't want.
I suggest that you read the virt-install documentation carefully, and if this still doesn't explain its behaviour and you think there's a bug in virt-install that incorrectly sets this flag, then to explain the details reassign this bug to "virtinst" and mark it as New.