Terminate user session to prevent strange behavior on confirmation

This pull request terminates the user session before it takes further action when a new password is requested or when the e-mail address of a newly registered user is confirmed. I changed it because it might cause strange behavior when a user is still logged in somehow. Furthermore I've replaced the use of the deprecated (in Symfony 2.4) ``getRequest`` function.

**Changes**
- Change to terminate user session to prevent strange behavior
- Update usage of deprecated getRequest function