Don't log in user after registration.

This obliges them to log in on the client.
Fixes #753.

Author: RubenVerborgh

lib/requests/create-account-request.js

@@ -127,7 +127,6 @@ class CreateAccountRequest extends AuthRequest {
       .then(this.cancelIfAccountExists.bind(this))
       .then(this.createAccountStorage.bind(this))
       .then(this.saveCredentialsFor.bind(this))
-      .then(this.initUserSession.bind(this))
       .then(this.sendResponse.bind(this))
       .then(userAccount => {
         // 'return' not used deliberately, no need to block and wait for email