Collision exclusion doesn't work when bodies are already colliding

[QbieShay]

Godot version

v4.0.dev.custom_build [60add98] - master branch July 16 2021

System information

Linux Arch, Radeon RX 590

Issue description

Collision exception doesn't work if the bodies are child of one another.

Steps to reproduce

Open mrp, launch the main scene.

Minimal reproduction project

Repro.zip

[pouleyKetchoupp]

It doesn't seem the issue is due to one being a child of the other one, but I can confirm there's an issue when setting a collision exception after the bodies already collide, because rigid bodies that are already sleeping don't get updated.

Note: In the repro project, the body path used for setting the exception is not correct, but after fixing it the exceptions still don't work when pressing the key, although they do when set in _ready() instead.