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/25fa71ae5ffd7e3d01e59acc0baaffd4c49e2bc0). 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.