NettyRpcServer is now our default RPC server replacing SimpleRpcServer.
To set the rpc server back to SimpleRpcServer, set 'hbase.rpc.server.impl' to org.apache.hadoop.hbase.ipc.SimpleRpcServer
HBASE-17263 added netty rpc server. This issue is about making it default given it has seen good service across two singles-days at scale. Netty handles the scenario seen in HBASE-19320 (See tail of HBASE-19320 for suggestion to netty the default)