Add detail to backup_restore remote storage docs

- Location in which to add `gitlab_rails` configurations
- Reminder to run `gitlab-ctl reconfigure` after changing gitlab_rails

doc/raketasks/backup_restore.md

@@ -91,7 +91,7 @@ In the example below we use Amazon S3 for storage, but Fog also lets you use
 for AWS, OpenStack Swift and Rackspace as well. A local driver is
 [also available](#uploading-to-locally-mounted-shares).
 
-For omnibus packages:
+For omnibus packages, add the following to `/etc/gitlab/gitlab.rb`:
 
 ```ruby
 gitlab_rails['backup_upload_connection'] = {
@@ -106,6 +106,8 @@ gitlab_rails['backup_upload_connection'] = {
 gitlab_rails['backup_upload_remote_directory'] = 'my.s3.bucket'
 ```
 
+Make sure to run `sudo gitlab-ctl reconfigure` after editing `/etc/gitlab/gitlab.rb` to reflect the changes.
+
 For installations from source:
 
 ```yaml