add Rule Discovery for Swarm

[dongdongking008]

service label: prometheus.rules.xxxRuleName: { "Alert": "HighCPURatio", "Expr": "os_cpu_used_ratio{service=\"{{.Service}}\"} > 0.7", "For": "30s", "Annotations": { "Summary": "High CPU Ratio on {{$labels.instance}}, current value: {{$value}}" } }