Added test case for starting rails with daemon option

[phedkvist]

Summary

Currently there is no test for testing that daemon is set correctly when provided by the user when starting rails using rails s -d. The two test cases makes sure that the options[:daemonize] is set to true when the argument -d is given.

[rails-bot]

Thanks for the pull request, and welcome! The Rails team is excited to review your changes, and you should hear from @georgeclaghorn (or someone else) soon.

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