New preconfig runstate will be used in follow up patches
related to introducing --preconfig CLI option and is
intended to replace prelaunch runstate from QEMU start
up to machine_init callback.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1525423069-61903-4-git-send-email-imammedo@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[ehabkost: Changed "since 2.13" to "since 3.0"]
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>