Bug 123042 When do some operation on the data drive manager, the eclipse may be broken.
Description: When do some operation on the data drive manager, the eclipse may be broken. Steps to reproduce: 1. new a JDBC data resource, and click the "Manage drivers" 2. delete a Jar file , and click "OK" 3. click the "Manage drivers" , add the deleted Jar File and click "OK" 4. click the "Manage drivers" and click the 'Drivers' tab, and set a 'Display name' and 'URL Template' and clcik 'OK' 5. click the "Manage drivers" and click the 'Drivers' tab, and delete the 'Display name' and 'URL Template' and clcik 'OK' Actual result: The eclipse is broken. Expect result: The eclipse runs in good shape.
data/org.eclipse.birt.report.data.oda.jdbc.ui/src/org/eclipse/birt/report/data/oda/jdbc/ui/util/JdbcToolKit.java
* Resets cached jdbc driver list to null, force reget the infomation when
	 * required next time.
	 */
	public static void resetJdbcDriverNames( )
	{
		jdbcDriverInfos = null;
		driverNameMap = null;
		file2Drivers = null;
	}
	 
	 /**
	  * Found drivers in the Jar file List
	  * @param file
	  * @return a List of JDBCDriverInformation
	  */
	public static void getJdbcDriverFromFile( List fileList )
	{
		URLClassLoader urlClassLoader = createClassLoader( fileList );
		jdbcDriverInfos.addAll( getJDBCDriverInfoList( fileList, urlClassLoader ) );
	}
	/**
	 * Returns a List jdbc Drivers. The Drivers are searched from predefined
	 * directories in the DTE plug-in. Currently it is expected that the jdbc
	 * drivers are in the "drivers" directory of the DTE oda.jdbc plug-in.
	 * @param driverName
	 * @return
	 */
	public static List getJdbcDriversFromODADir( String driverName )
	{
		if ( jdbcDriverInfos != null )