[routing] Assign junction:ref for link ways from motorway_junction node's ref.

[vng]

More details here: https://github.com/organicmaps/organicmaps/issues/849

[AntonM030481]

BTW similar approach can be used to set speed limit for speed camera from way speed limit. I have seen situations where road speed limit is set, but for speed cam on this road it is not set.