[test] don't leave NULL columns around when making an attribute required
It doesn't matter on sqlite (it doesn't do ALTER COLUMN), but when
running this test on postgresql it fails to add the 'NOT NULL'
constraint otherwise.
<html>
<head>
<!-- dependencies -->
<script type="text/javascript">
var JSON_BASE_URL = '';
</script>
<script type="text/javascript" src="../../data/jquery.js"></script>
<script src="../../data/cubicweb.js" type="text/javascript"></script>
<script src="../../data/cubicweb.htmlhelpers.js" type="text/javascript"></script>
<script src="../../data/cubicweb.python.js" type="text/javascript"></script>
<script src="../../data/cubicweb.compat.js" type="text/javascript"></script>
<script src="../../data/cubicweb.ajax.js" type="text/javascript"></script>
<!-- qunit files -->
<script type="text/javascript" src="../../../devtools/data/qunit.js"></script>
<link rel="stylesheet" type="text/css" media="all" href="../../../devtools/data/qunit.css" />
<!-- test suite -->
<script src="cwmock.js" type="text/javascript"></script>
<script src="test_ajax.js" type="text/javascript"></script>
</head>
<body>
<div id="main"> </div>
<h1 id="qunit-header">cubicweb.ajax.js functions tests</h1>
<h2 id="qunit-banner"></h2>
<ol id="qunit-tests">
</body>
</html>