test: console constructor missing new keyword

The `console.Console()` constructor function handles a missing `new`
keyword. This code is not exercised in the current tests. Add a test for
this.

PR-URL: nodejs#8003
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>
Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>
Reviewed-By: JacksonTian - Jackson Tian <shvyo1987@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-console-instance.js

@@ -64,3 +64,8 @@ out.write = function(d) {
 };
 [1, 2, 3].forEach(c.log);
 assert.equal(3, called);
+
+// Console() detects if it is called without `new` keyword
+assert.doesNotThrow(function() {
+  Console(out, err);
+});