will call pid file back

[Xiangdong Huang <sa...@gmail.com>]

Hi,
I notice we removed the pid file after the server starts, Maybe it is
because that pid file is not easy to be maintained.

But in many cases, pid file is useful, especially if we want to make
iotdb as a service in linux-like OS.

So, I'd like to revert the behavior that recording the pid into a file
after iotdb starts up.

Meanwhile, it is also ok to keep current check_running_process() in
start-server.sh, who uses "lsof -i: port" to check whether iotdb is
alive.

Best,
-----------------------------------
Xiangdong Huang
School of Software, Tsinghua University