[ROCKETMQ-308] Increasing name server component network socket buffer size (#199)

* [ROCKETMQ-308]  nameserver socket buffer use default value.

(cherry picked from commit e9fcb07)

* [ROCKETMQ-308]  delete unused import

(cherry picked from commit 3bcefff)

namesrv/src/main/java/org/apache/rocketmq/namesrv/NamesrvStartup.java

@@ -32,7 +32,6 @@ import org.apache.rocketmq.common.MixAll;
 import org.apache.rocketmq.common.constant.LoggerName;
 import org.apache.rocketmq.common.namesrv.NamesrvConfig;
 import org.apache.rocketmq.remoting.netty.NettyServerConfig;
-import org.apache.rocketmq.remoting.netty.NettySystemConfig;
 import org.apache.rocketmq.remoting.protocol.RemotingCommand;
 import org.apache.rocketmq.srvutil.ServerUtil;
 import org.apache.rocketmq.srvutil.ShutdownHookThread;
@@ -49,15 +48,6 @@ public class NamesrvStartup {
 
     public static NamesrvController main0(String[] args) {
         System.setProperty(RemotingCommand.REMOTING_VERSION_KEY, Integer.toString(MQVersion.CURRENT_VERSION));
-
-        if (null == System.getProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_SOCKET_SNDBUF_SIZE)) {
-            NettySystemConfig.socketSndbufSize = 4096;
-        }
-
-        if (null == System.getProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_SOCKET_RCVBUF_SIZE)) {
-            NettySystemConfig.socketRcvbufSize = 4096;
-        }
-
         try {
             //PackageConflictDetect.detectFastjson();