Update grafana to use persistent storage.

monitoring/docker-compose.yaml

@@ -21,6 +21,8 @@ volumes:
     name: influxdb
   prometheus-config:
     name: prometheus-config
+  grafana-data:
+    name: grafana-data
 
 services:
   netdata:
@@ -129,6 +131,8 @@ services:
     restart: unless-stopped
     depends_on:
       - influxdb
+    volumes:
+      - grafana-data:/var/lib/grafana
     networks:
       - proxy
       - internal