Fix a huge bug that was completely preventing login from succeeding

- Add the username and password *text* from the input fields to the
  login URL - before it was passing the UITextField object and erroring
  with "illegal username".
- Correctly pass cookies and session IDs to the rollback method and the
  two login queries.
- Instance variable-ise the has_rollback_permission? method, to
  correctly obtain the return value from the block.