Removed the hardcoded endpoint/shutdown URL

[chbwien]

The hardcoded endpoint/shutdown url was a security issue, because on public servers, the server could easily be shut down. I have therefore

• removed the hardcoded url action
• added the endpoint/shutdown in the standard restpsroutes.json

So now, one can use any urlö and any additional verification before the server is shut down.

[jpsider]

Had to remove a test that was looking for the endpoint.