Optimize HBase RPC Encryption Performance

Similar to HADOOP-10768, when HBase RPC encryption is enabled by setting hbase.rpc.protection to privacy, it does not use AES-NI acceleration by default.

We have implemented a workaround for HBase to use accelerated encryption that can be shown to improve performance, see https://rayokota.wordpress.com/2016/09/13/adventures-in-hardening-hbase/. I will attach a patch of the changes for our workaround, which borrows heavily from the patch for HADOOP-10768, but I'll leave it to the HBase security experts as to what is the best approach.