- [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.


static ServerBuilder buildServerBuilder(URL url, NettyServerBuilder builder) {
        int maxInboundMessageSize = url.getParameter(MAX_INBOUND_MESSAGE_SIZE, 0);
        if (maxInboundMessageSize > 0) {
            builder.maxInboundMessageSize(maxInboundMessageSize);
        }
        int maxInboundMetadataSize = url.getParameter(MAX_INBOUND_METADATA_SIZE, 0);
        if (maxInboundMetadataSize > 0) {
            builder.maxInboundMetadataSize(maxInboundMetadataSize);
        }
        if (url.getParameter(SSL_ENABLED_KEY, false)) {
            builder.sslContext(buildServerSslContext(url));
        }
        int flowControlWindow = url.getParameter(MAX_INBOUND_MESSAGE_SIZE, 0);
        if (flowControlWindow > 0) {
            builder.flowControlWindow(flowControlWindow);