GUI: link to former-parent is not rendered correctly / "Parent becomes Neighbor" event not emitted #731

Found: if a Child upgrades to Router, then the link to the former-parent is not rendered properly. It should be shown "thick" i.e. because the link is in the neighbors set, but it's shown thin. Reason is that the conversion of the link from former-parent link to router-neighbor-link is not sent as a "router added" event by OT.

Current workaround is for the GUI to catch the "to Router role" event and then assume the former-Parent will go into the neighbors list. Best for the future would be to render the ground truth as coming from the OT node, using a status push event.