Do not use `supervisor` to start/stop `node_exporter`.

cookbooks/prometheus-exporters/files/etc/supervisor/conf.d/node_exporter.conf

@@ -1,8 +0,0 @@
-[program:node_exporter]
-command=/usr/local/bin/node_exporter --web.listen-address="127.0.0.1:9100" -collector.systemd
-stdout_logfile=/var/log/supervisor/node_exporter.log
-redirect_stderr=true
-stdout_logfile_maxbytes=1MB
-stdout_logfile_backups=5
-autorestart=true
-stopsignal=HUP