Bug 24157 [Dialogs] MessageDialog needs to setFocus on default button
As the MessageDialog by default has no other widgets to set focus on we need to set focus on the default button to prevent it getting slammed by the default SWT behaviour.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/MessageDialog.java
* @param dialogTitle the dialog title, or <code>null</code> if none
 * @param dialogTitleImage the dialog title image, or <code>null</code> if none
 * @param dialogMessage the dialog message
 * @param dialogImageType one of the following values:
 * <ul>
 *	<li> <code>MessageDialog.NONE</code> for a dialog with no image </li>
 *	<li> <code>MessageDialog.ERROR</code> for a dialog with an error image </li>
 *	<li> <code>MessageDialog.INFORMATION</code> for a dialog with an information image </li>
 * 	<li> <code>MessageDialog.QUESTION </code> for a dialog with a question image </li>
 *	<li> <code>MessageDialog.WARNING</code> for a dialog with a warning image </li>
 * </ul>
 * @param dialogButtonLabels an array of labels for the buttons in the button bar
 * @param defaultIndex the index in the button label array of the default button
 */
public MessageDialog(Shell parentShell, String dialogTitle, Image dialogTitleImage, String dialogMessage, int dialogImageType, String[] dialogButtonLabels, int defaultIndex) {
	super(parentShell);
	this.title = dialogTitle;
	this.titleImage = dialogTitleImage;
	this.message = dialogMessage;
	switch (dialogImageType) {
		case ERROR : {
			this.image = getImage(DLG_IMG_ERROR);
			break;
		} 
		case INFORMATION : {
			this.image = getImage(DLG_IMG_INFO);
			break;
		} 
		case QUESTION : {
			this.image = getImage(DLG_IMG_QUESTION);