New centrality tests are failing

[gdalle]

The new centrality tests introduced by #272 seem to be responsible for CI failures in #268 (sorry @Dolgalad).
@simonschoelly any clue about this?

[simonschoelly]

I did not have time to look deeply into it, but I doubt that #272 is responsible for this, as tests have passed before.

[gdalle]

Ok, then it's probably the modification to Dijkstra that is to blame