If you continue to receive the above error, please note the following:
- This error occurs when there is still an update task running in the background. 

- Closing an update window does not end the update process, it will continue to run in the background until complete.

- If the server was online when the update was run, it will be started automatically after completing it. 

- This error will disappear once the background update has completed and you will see that the service is "Already Up to Date" in the Steam update window.

- You will also receive an error when trying to delete the Steamapps folder due to the files being in use from the updater. A force validation is not required in this situation