AETHER-686 Reboot when the serial device is not loaded

Also, don't reboot but restart the service when disconnect action failed.

Change-Id: Ia06bc73d0a2643ff8ca8737c7985fbf9825e37de
diff --git a/edge-monitoring/agent_modem/edge-mon-agent.service b/edge-monitoring/agent_modem/edge-mon-agent.service
index 1d6ba22..7fa743d 100644
--- a/edge-monitoring/agent_modem/edge-mon-agent.service
+++ b/edge-monitoring/agent_modem/edge-mon-agent.service
@@ -5,7 +5,7 @@
 [Service]
 Environment=CONFIG_FILE=/home/pi/aether-monitoring/edge-monitoring/agent_modem/config.json
 Type=simple
-ExecStartPre=/bin/sleep 30
+ExecStartPre=/bin/sleep 60
 ExecStart=/usr/bin/python3 /home/pi/aether-monitoring/edge-monitoring/agent_modem/edge_monitoring_agent_modem.py
 Restart=on-failure