Add note to ssh host keys section in geo docs

doc/administration/geo/replication/configuration.md

@@ -170,6 +170,11 @@ keys must be manually replicated to the **secondary** node.
    sudo service sshd reload
    ```
 
+1. Verify SSH is still functional.
+    
+   SSH into your GitLab **secondary** server in a new terminal. If you are unable to connect,
+   verify the permissions are correct according to the previous steps.
+
 ### Step 3. Add the **secondary** node
 
 1. SSH into your GitLab **secondary** server and login as root: