Fixed SIGQUIT not removing listening UNIX sockets (closes #753).
Fixed SIGQUIT not removing listening UNIX sockets (closes #753).

Listening UNIX sockets were not removed on graceful shutdown, preventing
the next runs.  The fix is to replace the custom socket closing code in
ngx_master_process_cycle() by the ngx_close_listening_sockets() call.

hy0kl/nginx,hy0kl/nginx,hy0kl/nginx