[ROCKETMQ-308] Increasing name server component network socket buffer size

[fuyou001]

What is the purpose of the change

Increasing name server component network socket buffer size, improve broker register speed, resolve the issue ROCKETMQ-308

Brief changelog

delete NamesrvStartup set network socket buffer code,using default value.

delete code

  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;
        }

[coveralls]

Coverage increased (+0.1%) to 38.896% when pulling d21a184 on fuyou001:ROCKETMQ-308 into 3a0451b on apache:master.

[zhouxinyu]

Thanks,
but please fork and merge your contribution to develop master, and use a meaningful title.

[zhouxinyu]

I changed the target branch, but it seems your PR is based on the wrong codebase, please help fix it.

[zhouxinyu]

Hi @fuyou001, It seems that only this commit should be merged, please help fix this PR.

[zhouxinyu]

duplicated.