Remove unnecessary check that child process was started

[github-actions]

This is an automatic cherry-pick of d0bd35befba56fb3db35f42e9db7069daa60cf85

The original PR was #222 with message:

Even if the child process dies immediately after being launched, the call to g_child_watch_add() will register a callback that will alert the application of the exit code when the main loop is reached.

In this case, status will briefly change to STATUS_RUNNING before changing to DOCKERD_RUNTIME_ERROR.

Checklist before requesting a review

• I have performed a self-review of my own code
• I have verified that the code builds perfectly fine on my local system
• I have added tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have verified that my code follows the style already available in the repository
• I have made corresponding changes to the documentation