bug: should delete conf/config_listen.sock if start failed

[tzssangglass]

Current Behavior

conf/config_listen.sock is not deleted after start failed

Expected Behavior

delete conf/config_listen.sock after start failed

Error Logs

nginx: [emerg] bind() to unix:/tmp/apisix300/conf/config_listen.sock failed (98: Address already in use)

Steps to Reproduce

1. use another process to listen on port 9080
2. starting APISIX , it reports nginx: [emerg] bind() to 0.0.0.0:9080 failed (98: Address already in use), which failed, but conf/config_listen.sock was created and not deleted
3. stop the process which listens on port 9080
4. starting APISIX again, which failed, it reports nginx: [emerg] bind() to unix:/tmp/apisix300/conf/config_listen.sock failed (98: Address already in use) because the conf/config_listen.sock created in step 2 was not deleted
5. After deleting conf/config_listen.sock, APISIX starts normally, and conf/config_listen.sock is deleted after normal shutdown

Environment

• APISIX version (run apisix version): master
• Operating system (run uname -a):
• OpenResty / Nginx version (run openresty -V or nginx -V):
• etcd version, if relevant (run curl http://127.0.0.1:9090/v1/server_info):
• APISIX Dashboard version, if relevant:
• Plugin runner version, for issues related to plugin runners:
• LuaRocks version, for installation issues (run luarocks --version):