Update dependent logical elements from user input in build model.

Direct links must have same vlan in both endpoints.
hus, when the user changes the vlan in an endpoint of a link,
opennaas should update the other endpoint with user given vlan.
Merge pull request #505 from isartcanyameres/feature/vcpe-buildmodel-update-dependent-logical-elements

Update dependent logical elements from user input in build model.