test: fix flaky test-vm-timeout-rethrow

The intention of test case is to make sure that `timeout` property is honored
and the code in context terminates and throws correct exception. However in
test case, the code inside context would complete before `timeout` for windows
and would sometimes fail. Updated the code so it guarantee to not complete
execution until timeout is triggered.

Fixes: https://github.com/nodejs/node/issues/11261
PR-URL: https://github.com/nodejs/node/pull/11530
Reviewed-By: James M Snell <jasnell.gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Josh Gavant <josh.gavant@outlook.com>

test/sequential/test-vm-timeout-rethrow.js

@@ -5,15 +5,9 @@ const vm = require('vm');
 const spawn = require('child_process').spawn;
 
 if (process.argv[2] === 'child') {
-  const code = 'let j = 0;\n' +
+  const code = 'while(true);';
-               'for (let i = 0; i < 1000000; i++) j += add(i, i + 1);\n' +
-               'j;';
 
-  const ctx = vm.createContext({
+  const ctx = vm.createContext();
-    add: function(x, y) {
-      return x + y;
-    }
-  });
 
   vm.runInContext(code, ctx, { timeout: 1 });
 } else {