vscode (maybe lsp?): Registering dynamically and statically causes duplicate requests

[david-driscoll]

So 0.3.0 fixed an issue with the client options providers not working as expected.

This has raised a new issue, where providers registered via the static means (at client return) are also called again when dynamically registered.

Need to investigate this issue and see if it's a problem in LSP implementation, the vscode lsp implementation or just a regular bug.

cc @tintoy

[tintoy]

Probably vscode-languageclient, BTW - I found I got double-called for stuff like hover and completions if I added a DocumentSelector twice on the LanguageClient in my extension :)