Fix disaster recovery instructions

doc/gitlab-geo/disaster-recovery.md

 # GitLab Geo Disaster Recovery
 
 > **Note:**
-This is not officially supported yet, please don't use as your only 
+This is not officially supported yet, please don't use as your only
 Disaster Recovery strategy as you may loose data.
 
 GitLab Geo replicates your database and your Git repositories. We will
 support and replicate more data in the future, that will enable you to
-fail-over with minimal effort, in a disaster situation. 
+fail-over with minimal effort, in a disaster situation.
 
-See [current limitations](README.md#current-limitations) 
+See [current limitations](README.md#current-limitations)
 for more information.
 
 
@@ -19,19 +19,38 @@ but you can do it manually if you have `root` access to the machine.
 
 You must make the changes in the exact specific order:
 
-1. Take down your primary node (or make sure it will not go up during this 
+1. Take down your primary node (or make sure it will not go up during this
    process or you may loose data)
 2. Wait for any database replication to finish
 3. Promote the Postgres in your secondary node as primary
 4. Log-in to your secondary node with a user with `sudo` permission
 5. Open the interactive rails console: `sudo gitlab-rails console` and execute:
-    1. `Gitlab::Geo.primary_node.oauth_application.destroy!`
-    2. `Gitlab::Geo.primary_node.system_hook.destroy!`
-    3. `Gitlab::Geo.primary_node.update(primary: false)`
-    4. List your secondary nodes and note down the id of the one you want to 
-       promote: `Gitlab::Geo.secondary_nodes`
-    5. To promote a node with id `2` execute: 
-       `GeoNode.find(2).update!(primary: true)`
-    6. To exit the interactive console, type: `exit`
-6. Rsync everything in `/var/opt/gitlab/gitlab-rails/uploads` and 
+    1. List your primary node and note down it's id:
+       ```ruby
+       Gitlab::Geo.primary_node
+       ```
+    2. Turn your primary into a secondary:
+       ```ruby
+       Gitlab::Geo.primary_node.update(primary: false)
+       ```
+    3. List your secondary nodes and note down the id of the one you want to
+       promote:
+       ```ruby
+       Gitlab::Geo.secondary_nodes
+       ```
+    4. To promote a node with id `2` execute:
+       ```ruby
+       GeoNode.find(2).update!(primary: true)
+       ```
+    5. Now you have to cleanup your new promoted node by running:
+       ```ruby
+       Gitlab::Geo.primary_node.oauth_application.destroy!
+       Gitlab::Geo.primary_node.system_hook.destroy!
+       ```
+    6. And refresh your old primary node to behave correctly as secondary (assuming id is `1`)
+       ```ruby
+       GeoNode.find(1).save!
+       ```
+    7. To exit the interactive console, type: `exit`
+6. Rsync everything in `/var/opt/gitlab/gitlab-rails/uploads` and
    `/var/opt/gitlab/gitlab-rails/shared` from your old node to the new one.