Fix TOTP authentication

Summary:
Kolab used to depend on version 4 of the otphp library, which returns
its computed OTP codes as integers. Hence, the kolab_2fa plugin converts
the user input to `int` in order to facilitate comparisons using the
`===` operator.

Starting with version 5, which is now bundled with Kolab, otphp returns
a string instead of an integer. Now the comparison is between an `int`
and a `string`, and thus consistently yields `false`. As a result, no
TOTP code is ever accepted.

Fix TOTP authentication by removing the now-obsolete conversion to
`int`.

Reviewers: machniak

Reviewed By: machniak

Differential Revision: https://git.kolab.org/D4370

plugins/kolab_2fa/lib/Kolab2FA/Driver/TOTP.php

@@ -77,9 +77,6 @@ class TOTP extends Base
 
         $this->backend->setLabel($this->username)->setSecret($secret);
 
-        // PHP gets a string, but we're comparing integers.
-        $code = (int)$code;
-
         // Pass a window to indicate the maximum timeslip between client (mobile
         // device) and server.
         $pass = $this->backend->verify($code, $timestamp, 150);