[Chef 11.10] Don't define a restart command unless the current instance is in the "rails-app" layer

This pull request makes the `opsworks_deploy` resource not define a restart command unless it is running on a `rails-app` instance. This means that on instances that have a copy of the Rails app, but not running a web server (like a Sidekiq, Clockwork, etc. layer), it won't try to restart Unicorn/Passenger.

License: Public Domain. Do whatever you want with this PR, including relicensing under any other license.