Fix JS syntax issues

[bmontuelle]

Good morning/afternoon

While trying to implement OAuth2 token introspection using Nginx Plus, I had to change a few lines in the oauth2.js script to get it to work.

There is no length property on javascript primitive type boolean, it returns undefined everytime and never enter the bloc

if (response.active.length) {

In here, response is the object representation of the introspection response. Encoding it in base64 will in fact encode [Object object] I encoded the responseBody bytes instead

response.toString('base64')

From what I was able to test caching works fine and no issue with decoding the introspection being from server response or cached value.

Cheers,
Benoit