Fix #2295 - Respond to initialize with an initialized message

test/lsp/test_did_save_event.vader

@@ -38,10 +38,10 @@ Before:
     let g:conn_id = ale#lsp#Register('executable', '/foo/bar', {})
     call ale#lsp#MarkDocumentAsOpen(g:conn_id, a:buffer)
     let l:details = {
+    \ 'command': 'foobar',
     \ 'buffer': a:buffer,
     \ 'connection_id': g:conn_id,
     \ 'project_root': '/foo/bar',
-    \ 'language_id': 'foobar',
     \}
 
     call a:Callback(a:linter, l:details)