Issue description

If I use make run to start multiple apisix server, the process shows below:
[nero@VM_42_81_centos ~/incubator-apisix]$ ps -ef | grep apisix
nero 28293 1 0 10:35 ? 00:00:00 nginx: master process /usr/local/openresty/bin/openresty -p /home/nero/incubator-apisix/ -c /home/nero/incubator-apisix/conf/nginx.conf
nero 29053 1 0 10:40 ? 00:00:00 nginx: master process /usr/local/openresty/bin/openresty -p /home/nero/incubator-apisix/ -c /home/nero/incubator-apisix/conf/nginx.conf

Now if i use make stop to stop a apisxi server , it goes ok
[nero@VM_42_81_centos ~/incubator-apisix]$ make stop
/usr/local/openresty/bin/openresty -p $PWD/ -c $PWD/conf/nginx.conf -s stop
[nero@VM_42_81_centos ~/incubator-apisix]$ ps -ef | grep apisix
nero 28293 1 0 10:35 ? 00:00:00 nginx: master process /usr/local/openresty/bin/openresty -p /home/nero/incubator-apisix/ -c /home/nero/incubator-apisix/conf/nginx.conf
nero 29362 28108 0 10:42 pts/0 00:00:00 grep --color=auto apisix

But if is make stop again, it produce a error message
[nero@VM_42_81_centos ~/incubator-apisix]$ make stop
/usr/local/openresty/bin/openresty -p $PWD/ -c $PWD/conf/nginx.conf -s stop
nginx: [error] open() "/home/nero/incubator-apisix/logs/nginx.pid" failed (2: No such file or directory)
make: *** [stop] Error 1
[nero@VM_42_81_centos ~/incubator-apisix]$ ps -ef | grep apisix
nero 28293 1 0 10:35 ? 00:00:00 nginx: master process /usr/local/openresty/bin/openresty -p /home/nero/incubator-apisix/ -c /home/nero/incubator-apisix/conf/nginx.conf
nero 29421 28108 0 10:42 pts/0 00:00:00 grep --color=auto apisix

and the another apisix process remains
I think this is a bug if some one missuse this command

Environment

• apisix version (cmd: apisix version):
• OS:

Minimal test code / Steps to reproduce the issue

1. make run
2. make run
3. make stop

What's the actual result? (including assertion message & call stack if applicable)

What's the expected result?