Support symlinked public/uploads for backp restore

The backup restore code moves any existing uploads directory out of the
way before restoring the copy from the backup. If public/uploads was a
symlink, this move would replace the symlink. This commit avoids this
issue by first resolving any symlinks in the uploads path.

lib/backup/uploads.rb

@@ -3,7 +3,7 @@ module Backup
     attr_reader :app_uploads_dir, :backup_uploads_dir, :backup_dir
     def initialize
-      @app_uploads_dir = Rails.root.join('public', 'uploads')
+      @app_uploads_dir = File.realpath(Rails.root.join('public', 'uploads'))
       @backup_dir = Gitlab.config.backup.path
       @backup_uploads_dir = File.join(Gitlab.config.backup.path, 'uploads')
     end
@@ -21,8 +21,9 @@ module Backup
     end
     def backup_existing_uploads_dir
+      timestamped_uploads_path = File.join(app_uploads_dir, '..', "uploads.#{Time.now.to_i}")
       if File.exists?(app_uploads_dir)
-        FileUtils.mv(app_uploads_dir, Rails.root.join('public', "uploads.#{Time.now.to_i}"))
+        FileUtils.mv(app_uploads_dir, timestamped_uploads_path)
       end
     end
   end