[service] allow repo_stats for users
It's used by the siteinfo view, which is available to managers and
users. This change prevents a crash in that view.
<div id="ajaxroot">
<div class="ajaxHtmlHead">
<script src="http://foo.js" type="text/javascript"> </script>
<link rel="stylesheet" type="text/css" media="all" href="qunit.css" />
</div>
<h1>Hello</h1>
</div>