[FIX] nonReadRequests middleware: Use native response API

Using the native "statusCode" property instead of the express method to
set the status code to allow using the middleware with a different server
framework or as a native Node.js server handler.

This also aligns with other existing middleware that set the statusCode.

lib/middleware/nonReadRequests.js

@@ -12,7 +12,8 @@ function createMiddleware() {
 		// Handle anything but read operations *before* the serveIndex middleware
 		//	as it will reject them with a 405 (Method not allowed) instead of 404 like our old tooling
 		if (req.method !== "GET" && req.method !== "HEAD" && req.method !== "OPTIONS") {
-			res.status(404).end(`Cannot ${req.method} ${req.url}`);
+			res.statusCode = 404;
+			res.end(`Cannot ${req.method} ${req.url}`);
 		} else {
 			next();
 		}

test/lib/server/middleware/nonReadRequests.js

@@ -29,13 +29,10 @@ test("Non read requests results in status 404 and an error message", (t) => {
 	const methods = ["POST", "PUT", "DELETE"];
 	methods.forEach(function(method) {
 		res = {
-			status: function(status) {
-				t.deepEqual(status, 404, "Status should be 404");
-				return {
-					end: function(message) {
-						t.deepEqual(message, "Cannot " + method + " /somePath", "Finished with error message.");
-					}
-				};
+			statusCode: 200,
+			end: function(message) {
+				t.deepEqual(res.statusCode, 404, "Status should be 404");
+				t.deepEqual(message, "Cannot " + method + " /somePath", "Finished with error message.");
 			}
 		};