lib/backup: fix broken permissions when creating repo dir

This commit fixes a typo where the mode argument to FileUtils.mkdir()
would be passed in decimal rather than octal format, yielding bad
permissions.

CHANGELOG

@@ -37,6 +37,9 @@ v 8.12.0 (unreleased)
   - Use the default branch for displaying the project icon instead of master !5792 (Hannes Rosenögger)
   - Adds response mime type to transaction metric action when it's not HTML
+v 8.11.4 (unreleased)
+  - Fix broken gitlab:backup:restore because of bad permissions on repo storage !6098 (Dirk Hörner)
+
 v 8.11.3 (unreleased)
   - Allow system info page to handle case where info is unavailable
   - Label list shows all issues (opened or closed) with that label

lib/backup/repository.rb

@@ -55,7 +55,7 @@ module Backup
         bk_repos_path = File.join(path, '..', 'repositories.old.' + Time.now.to_i.to_s)
         FileUtils.mv(path, bk_repos_path)
         # This is expected from gitlab:check
-        FileUtils.mkdir_p(path, mode: 2770)
+        FileUtils.mkdir_p(path, mode: 02770)
       end
       Project.find_each(batch_size: 1000) do |project|