fix: use logger from PluginLoggerMixin

lib/fluent/plugin/out_datadog.rb

@@ -141,7 +141,7 @@ def write(chunk)
         end
       end
     rescue Exception => e
-      @logger.error("Uncaught processing exception in datadog forwarder #{e.message}")
+      log.error("Uncaught processing exception in datadog forwarder #{e.message}")
     end
   end
 
@@ -286,6 +286,8 @@ def send_retries(payload, max_retries, max_backoff)
           backoff = 2 * backoff unless backoff > max_backoff
           retries += 1
           retry
+        else
+          raise e
         end
       end
     end