Fixes the Codestyle

Hi @alikon  this PR fixes the CS issues for your PR see: https://travis-ci.org/joomla/joomla-cms/jobs/44127970

```
FILE: ...d/joomla/joomla-cms/administrator/components/com_users/models/users.php
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FOUND 5 ERROR(S) AFFECTING 3 LINE(S)
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 393 | ERROR | Concat operator must be preceeded by one space
 399 | ERROR | Concat operator must be preceeded by one space
 400 | ERROR | Concat operator must be followed by one space
 400 | ERROR | Concat operator must be preceeded by one space
 400 | ERROR | Concat operator must be preceeded by one space
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```