fix bug about feign and update examples

spring-cloud-alibaba-examples/nacos-example/nacos-discovery-example/nacos-discovery-consumer-example/scripts/feign-error.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+n=1
+while [ $n -le 10 ]
+do
+    echo `curl -s http://localhost:18083/divide-feign?a=1\&b=0`
+    let n++
+done

spring-cloud-alibaba-examples/nacos-example/nacos-discovery-example/nacos-discovery-consumer-example/src/main/resources/degraderule.json

@@ -16,5 +16,11 @@
     "count": 20.0,
     "grade": 0,
     "timeWindow": 30
+  },
+  {
+    "resource": "GET:http://service-provider/divide",
+    "count": 0.5,
+    "grade": 1,
+    "timeWindow": 30
   }
 ]