Sending a PR for Rust Coreutils; fixing a bug related to "no pid" when killing a process

Описание: Recently I'm enjoying studying the coreutils source code. And doing minor contributions to the project. Today I started working on something very straightforward and thought to share it with you.

This is the case: when the coreutils `kill` command is called with no pid, it returns a wrong value. It is written in rust so its more fun to work on. Lets fix it and submit a PR to the devs.