- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.6
* Operating System version: CentOS-7
* Java version: 1.8.0_275

### Steps to reproduce this issue

dobbo use netty to listen as a server .  and use this class SslConfig.java  and netty4/SslContexts.java to use ssl cert file .
this class always open file .
by netty's source :  PemReader and SslContextBuilder they not close this InputStream yet .and netty expect user close the InputStream if the InputStream is open by user.

https://github.com/netty/netty/issues/10974
https://github.com/netty/netty/pull/10976

but it seems dobbo not close it ?

![image](https://user-images.githubusercontent.com/5086059/106403950-e61ef980-646b-11eb-9d8d-2c21550e4954.png)

![image](https://user-images.githubusercontent.com/5086059/106403961-ecad7100-646b-11eb-929e-5ec79837886d.png)

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

InputStream maybe need close immediately?

### Actual Result

InputStream seems leak.


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package org.apache.dubbo.rpc.protocol.grpc;
import io.grpc.CallOptions;
import io.grpc.ManagedChannel;
import io.grpc.ServerBuilder;
import io.grpc.netty.GrpcSslContexts;
import io.grpc.netty.NettyChannelBuilder;
import io.grpc.netty.NettyServerBuilder;
import io.netty.handler.ssl.ClientAuth;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import org.apache.dubbo.common.URL;
import org.apache.dubbo.common.extension.ExtensionLoader;