Update server URL: corner case with opened trace view(s) on one server but not the other

While testing https://github.com/eclipse-cdt-cloud/vscode-trace-extension/issues/229 I noticed that changing the server URL with some trace views opened, they would sometimes be updated with a confusing message.

To reproduce:

- start 2 trace servers, on two machines or using a different port and workspace on the same machine
- use the URL of server 1, open a trace
- change URL to server 2 where the trace is not opened
- the opened trace is updated with the following text: "Trace loaded successfully. To see available views, open the Trace Viewer."
- I think it's good that the trace view is updated in a way to show that it's not currently opened in the current trace server, but the text in the view seems to have been intended for a different use-case?

If you switch back to server1 URL, the trace view is correctly restored.