Improvement for opendistro-for-elasticsearch opendistro-for-elasticse…

…arch#49

Reststatus.Created for WebHook-Response is also acceptable

notification/src/main/java/com/amazon/opendistroforelasticsearch/alerting/destination/client/DestinationHttpClient.java

@@ -153,7 +153,7 @@ public String getResponseString(CloseableHttpResponse response) throws IOExcepti
     private void validateResponseStatus(HttpResponse response) throws IOException {
         int statusCode = response.getStatusLine().getStatusCode();
 
-        if (statusCode != RestStatus.OK.getStatus()) {
+        if (!(statusCode == RestStatus.OK.getStatus() || statusCode == RestStatus.CREATED.getStatus())) {
             throw new IOException("Failed: " + response);
         }
     }