scm: filesystem: replace RAILS_ROOT to Rails.root in unit adapter test.

git-svn-id: https://svn.redmine.org/redmine/trunk@6053 e93f8b46-1217-0410-a6f0-8f06a7374b81

test/unit/lib/redmine/scm/adapters/filesystem_adapter_test.rb

@@ -2,8 +2,7 @@
 require File.expand_path('../../../../../../test_helper', __FILE__)
 
 class FilesystemAdapterTest < ActiveSupport::TestCase
-
-  REPOSITORY_PATH = RAILS_ROOT.gsub(%r{config\/\.\.}, '') + '/tmp/test/filesystem_repository'
+  REPOSITORY_PATH = Rails.root.join('tmp/test/filesystem_repository').to_s
 
   if File.directory?(REPOSITORY_PATH)
     def setup