Failed to check node env due to polyfill.

I am using axios on node.js (4.x). It has the logic that checks if node env.
It failed because of polyfill.
```js
function getDefaultAdapter() {
var adapter;

if (typeof XMLHttpRequest !== 'undefined') {
// For browsers use XHR adapter
adapter = xhr;
} else if (typeof browser$1 !== 'undefined' && Object.prototype.toString.call(browser$1) === '[object process]') {
// For node use HTTP adapter
adapter = http_1;
}
console.log("getDefaultAdapter", adapter,)
return adapter;
}
```
browser$1 is defined by `polyfills/process-es6.js`. But I think we should not inject it if using node.js.
```js
var browser$1 = {
nextTick: nextTick,
title: title,
browser: browser,
env: env,
argv: argv,
version: version,
versions: versions,
on: on,
addListener: addListener,
once: once,
off: off,
removeListener: removeListener,
removeAllListeners: removeAllListeners,
emit: emit,
binding: binding,
cwd: cwd,
chdir: chdir,
umask: umask,
hrtime: hrtime,
platform: platform,
release: release,
config: config,
uptime: uptime
};
```