MotionPlanner: Cosmetic change.
MotionPlanner: Fix incorrect speed in planning.

The speed at a junction should be limited by all of the following:
- Max speed of preceding segment.
- Max speed of folowing segment.
- Max speed due to cornering.

The second part of that list was missing until now.

Hopefully this is fixed once and for all. Regression test for the core planning algorithm will come soon.