MDL-43341 SCORM module report: Replaced usage of mod/scorm/pix/spacer.gif with moodle/pix/spacer.gif

The spacer image (/srv/http/moodle/mod/scorm/pix/spacer.gif) has some problem and it is not being displayed by chrome correctly.
SCORM code to generate spacer uses $OUTPUT->spacer() instead of  $OUTPUT->pix_url('spacer', 'scorm')