[autoboot] Display image information as part of the default control flow

When booting without an embedded script, display the imgstat()
information immediately before executing the downloaded image.  This
allows potentially useful diagnostic information (such as the detected
image type) to be observed by the user without needing to enter the
iPXE shell and manually download the image.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/usr/autoboot.c

 	if ( filename ) {
 		if ( ( rc = imgdownload ( filename, 0, &image ) ) != 0 )
 			goto err_download;
+		imgstat ( image );
 		image->flags |= IMAGE_AUTO_UNREGISTER;
 		if ( ( rc = image_exec ( image ) ) != 0 ) {
 			printf ( "Could not boot image: %s\n",