Lagrangian tracking can hang for particle exactly on cell centre

If a particle gets seeded on exactly the cell centre (e.g. in particle::locate) the tracking might get stuck in a loop since all constituent tets all say the particle is outside.

closed via commit 00ab1a10587f92398a07799e3ba050cc1bb59216

mentioned in commit 00ab1a10587f92398a07799e3ba050cc1bb59216

(just for cross reference: EP#741)

mentioned in commit 5ff5b0af