Changed opennms-datasources.xml parsing so that it is separated from the utility
classes that allow easy access to a singleton DataSource/XADataSource. Updated the
configs so that they specify AtomikosDataSourceFactory as the default DataSource.
Updated the test listeners so that the utility classes close the data sources
properly after test execution.
Removed unnecessary calls to DataSourceFactory.init(). This class works now
without being explicitly initialized.