Merge pull request rails#8282 from arunagw/warning_removed_for_ruby2

Initialize accessors to remove some warnings in Ruby 2.0

Author: carlosantoniodasilva

railties/lib/rails/engine.rb

@@ -407,6 +407,8 @@ def find(path)
       end
     end
 
+    self.isolated = false
+
     delegate :middleware, :root, :paths, to: :config
     delegate :engine_name, :isolated?, to: "self.class"