Particle shadows work only with directional light

[eon-s]

**Godot version: master ed6baff **

Issue description:
Particle shadows from omni and spot lights are updated only once (in editor and maybe running, hard to tell), they work fine with directional light.

Steps to reproduce:
Create an omni and/or spotlight that makes particles to projects shadows.
Do the same with a directional light.

Link to minimal example project:
particleshadow.zip

[reduz]

This bug is great, because it shows shadows are updated when geometry around changes, which is correct and a fanastic feature. Except it seems it's not working for particles, so fixing.