httplib: add Close() method to shut the server down and use it in tests

cmd/serve/httplib/http_new.go

@@ -14,3 +14,8 @@ func initServer(s *http.Server) {
 	s.ReadHeaderTimeout = 10 * time.Second // time to send the headers
 	s.IdleTimeout = 60 * time.Second       // time to keep idle connections open
 }
+
+// closeServer closes the server in a non graceful way
+func closeServer(s *http.Server) error {
+	return s.Close()
+}