use DelegatedNetwork as service name for java (Azure#13660)

Author: weidongxu-microsoft

specification/dnc/resource-manager/readme.md

@@ -99,6 +99,8 @@ These settings apply only when `--java` is specified on the command line.
 Please also specify `--azure-libraries-for-java-folder=<path to the root directory of your azure-libraries-for-java clone>`.
 
 ``` yaml $(java)
+service-name: DelegatedNetwork
+
 azure-arm: true
 fluent: true
 namespace: com.microsoft.azure.management.DelegatedNetwork