check for null values on account data in user service

This PR addresses https://optimizely.atlassian.net/browse/MKT-849 Account for false positive Optimizely signed in cookie in pricing.js.  See the line descriptions below for code description of what was actually changed.

To test, in the Gruntfile change the paths in /account/info to access index[1], and change the response for last 5 experiments to be `400`.  This mimics the production behavior is the `optimizely_signed_in` cookie exists, an object of accountData will be returned with null values, and the request for last 5 experiments will fail.  In testing you actually won't be able to tell ad difference because we are not removing the cookie.  This would take another PR, some syncing with adept, and potentially loading the jQuery cookie library synchronously before the user service.  

What this PR will address is getting stuck in a strange state that was reported on the pricing page for the `updatePlanInfo` function that is checking if the acctData exists.

```js
else if(req.url === '/account/info') {
     var paths = [
          'website-guts/endpoint-mocks/accountInfo.json',
           'website-guts/endpoint-mocks/nullAccountInfo.json'
      ];

       res.writeHead(200, {'Content-Type': 'application/json'});
       res.end( grunt.file.read(paths[1]) );

} else if(req.url === '/experiment/load_recent?max_experiments=5') {

   res.writeHead(400, {'Content-Type': 'application/json'});
    res.end( grunt.file.read('website-guts/endpoint-mocks/lastFiveExperiments.json') );
}
```