Change upstart script:

- Respawn and unlimited number of times
- Wait 60 seconds before restarting
Logic is to give whatever cause the process to fail some time to fix.  And to keep trying.

poller-service.conf

@@ -12,9 +12,15 @@ stop on runlevel [016]
 # Automatically restart process if crashed
 respawn
 
+# Restart an unlimited amount of times
+respawn limit unlimited
+
 chdir /opt/librenms
 setuid librenms
 setgid librenms
 
 # Start the process
 exec /opt/librenms/poller-service.py
+
+# Wait 60 seconds before restart
+post-stop exec sleep 60