remove preconfig state

remove preconfig state

The preconfig state is only used if -incoming is not specified, which
makes the RunState state machine more tricky than it need be.  However
there is already an equivalent condition which works even with -incoming,
namely qdev_hotplug.  Use it instead of a separate runstate.

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>