This was introduced earlier to indicate FairPlay protection system. But
in fact, it is sufficient to just use the system id for the indication.
- Also updated various parts of the pipeline to support empty PSSH.
- Added an additional FairPlay end to end test using fMP4.
Change-Id: Ica48b7b5235e9a2b5a7f722bcd0fc1ef2073ac13
KongQun Yang