Extract method refactoring for Rails::Server#start

The `start` method is large enough to consider being refactored. It consists of 4 non related pieces of code that can be extracted into private methods as shown in this [commit](https://github.com/notalex/rails/commit/6c244dd5fc6e02f280cbcb2acef61f2fa44071bd). I have introduced just a single method extraction here as I would like to discuss before extracting more methods out of `start`. We can discuss whether we need all 4 of the method extractions or some or none.