growisofs: Fix burning BD-R media not working
The BD-R flags were simply never applied to the plugin, so the brasero core didn't know how to burn that type of media.
See https://bugzilla.redhat.com/show_bug.cgi?id=1704341 and https://bugzilla.redhat.com/show_bug.cgi?id=1456971
Closes: #324 (closed)