fixes the `block_removed_ldap_users` rake task

Created by: MrMarvin

In e23a26ae (and later 1bc99369) the API for Gitlab::LDAP::Adapter was changed. I assume this rake task was an oversight in the refactoring of the changed class.

While being on it, I noticed that already blocked users cannot be blocked again.

Created by: TeatroIO

I've prepared a stage. Click to open.

By Administrator on 2014-11-12T11:17:53 (imported from GitLab project)

By Administrator on 2014-11-12T11:17:53 (imported from GitLab)

Created by: Razer6

/cc @jacobvosmaer

By Administrator on 2014-11-12T11:38:42 (imported from GitLab project)

By Administrator on 2014-11-12T11:38:42 (imported from GitLab)

Created by: jacobvosmaer

Thanks @MrMarvin !

By Administrator on 2014-11-12T12:40:46 (imported from GitLab project)

By Administrator on 2014-11-12T12:40:46 (imported from GitLab)