oraclejdk: use working mirror for download

http://download.oracle.com/otn-pub/ was recently renamed to
http://download.oracle.com/otn/ and now requires authentication with an
Oracle account. http://download.oracle.com/otn-pub/ links don't work
anymore, so installing oraclejdk fails.

Switch to http://javadl.oracle.com/webapps/download/GetFile/, which does
not require authentication. This fixes installing oraclejdk.

Note: The URL for JCE is still broken; this commit only fixes the URL
for the JDK.