Adapt Paperclip config for tests changes in dummy app initializer

When eager loading in CI, we need to make sure that changes to
Paperclip default config are applied before the file models are
loaded.

REDMINE-20487

spec/support/pageflow/dummy/app.rb

@@ -18,7 +18,6 @@ def generate
         end
 
         require(File.join(ENV['RAILS_ROOT'], 'config', 'environment'))
-        require('pageflow/dummy/config/pageflow')
       end
 
       def directory

spec/support/pageflow/dummy/config/pageflow.rb

@@ -14,6 +14,3 @@
     }
   end
 end
-
-# Reconstruct current config to ensure config block above is used
-Pageflow.configure!

spec/support/pageflow/dummy/rails_template.rb

@@ -69,6 +69,12 @@ def source_paths
   ActiveAdmin.application.load_paths.unshift(Dir[Rails.root.join('app/admin')].first)\n
 END
 
+# Adapt default configuration
+
+inject_into_file('config/initializers/pageflow.rb',
+                 "require 'pageflow/dummy/config/pageflow'\n",
+                 after: "Pageflow.finalize!\n")
+
 # Add required files for test theme
 
 copy_file('test_theme.scss',