[2.3][Process] Fix unit tests in sigchild disabled environment

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

We've been a bit fast when merging #10480 and tests were broken in the last update I did.