test: make HTTP/1.0 connection test more robust

Fixes: #47200

Co-authored-by: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-http-remove-connection-header-persists-connection.js

@@ -10,6 +10,13 @@ const server = http.createServer(function(request, response) {
   // For HTTP/1.0, the connection should be closed after the response automatically.
   response.removeHeader('connection');
 
+  if (request.httpVersion === '1.0') {
+    const socket = request.socket;
+    response.on('finish', common.mustCall(function() {
+      assert.ok(socket.writableEnded);
+    }));
+  }
+
   response.end('beep boop\n');
 });
 
@@ -50,9 +57,7 @@ function makeHttp10Request(cb) {
                 '\r\n');
     socket.resume(); // Ignore the response itself
 
-    setTimeout(function() {
-      cb(socket);
-    }, common.platformTimeout(50));
+    socket.on('close', cb);
   });
 }
 
@@ -62,9 +67,7 @@ server.listen(0, function() {
       // Both HTTP/1.1 requests should have used the same socket:
       assert.strictEqual(firstSocket, secondSocket);
 
-      makeHttp10Request(function(socket) {
-        // The server should have immediately closed the HTTP/1.0 socket:
-        assert.strictEqual(socket.closed, true);
+      makeHttp10Request(function() {
         server.close();
       });
     });