title: Passport JS Google OAuth2 - force login or account chooser
body: <p>I have google login in my service written in nodejs+express and use passport-google-oauth to log in with google. 
  On my site, I have a 'Sign in with Google' button. What I want, is to always show google login or Account Chooser when user hits this button. Instead, if I am logged in at exactly one google account in my browser, I immediately get logged in to service with this account. I've tried something like this when defining GoogleStrategy: </p>
  
  <pre><code>passport.use(new GoogleStrategy({
          clientID: GOOGLE_CLIENT_ID,
          clientSecret: GOOGLE_CLIENT_SECRET,
          callbackURL: REDIRECT_URL,
          passReqToCallback : true,
          prompt: 'select_account' // &lt;--!!!
      }, function(req, accessToken, refreshToken, profile, done) {
         //callback stuff
     })
  
  })
  </code></pre>
  
  <p>but it does not seem to work.</p>