RFR(XS): 8016444: Duplicate zombie check in safe_for_sender

[Rickard Bäckman]

Hi,

can I please have a couple of reviews for this small change. 
Basically we managed to get a merge error in the code and have two identical checks after each other.

I also got a heads up saying that we missed to update the copyright year in referenceProcessorStats.hpp so I fixed that in this change as well.

Webrev: http://cr.openjdk.java.net/~rbackman/8016444/

Thanks
/R