[12] RFR: JDK-8213837: FX samples cannot load media from download.java.net over http

[Kevin Rushforth]

Please review the following fix:

https://bugs.openjdk.java.net/browse/JDK-8213837
http://cr.openjdk.java.net/~kcr/8213837/webrev.00/

This changes "http://download.java.net" to "https://download.java.net"
in Ensemble8 and HelloMedia. Downloading via http has recently started
to fail, so we need to use https instead.

-- Kevin