Fix rake task redmine_s3:files_to_s3 to match the expected pathname.

Related to a7d4ae1e3483f3c41417078a17a43acb041fe908 which changed the
application's behavior.
Merge pull request #13 from flavorjones/fix-upload-rake-task

Fix rake task redmine_s3:files_to_s3 to match the expected pathname.