LPS-47041 Fix tests

Hi @mdelapenya, could you please verify if this PR fixes the problem that is happening on http://ci.liferay.org.es/jenkins/job/liferay-portal-master/2066/testReport/junit/com.liferay.portlet.dynamicdatamapping.util/DDMFormXSDSerializerTest/testDDMFormSerialization/? 

I couldn't reproduce the same issue on my machine but I think this commit fixes the problem. Please forward this to Brian if it ok.

cc @cgoncas

Thanks a lot!