fix cAdvisor container discovery by mounting /sys and /var/lib/docker correctly

monitoring/docker-compose.yml

@@ -39,9 +39,8 @@ services:
     restart: unless-stopped
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock:ro
-      - /proc:/host/proc:ro
-      - /sys:/host/sys:ro
-      - /:/rootfs:ro
+      - /sys:/sys:ro
+      - /var/lib/docker/:/var/lib/docker:ro
     command:
       - --docker_only=true
       - --housekeeping_interval=30s