Fix channel leakage in NettyConnectionClient.onConnected and onGoaway methods

[hanpen24]

What is the purpose of the change

fixe #14097
This commit addresses the issue of channel leakage in the onConnected and onGoaway methods of NettyConnectionClient.

Previously, channels were not properly closed when new channels were set or when the channels were marked as go away, leading to potential resource leaks.

Brief changelog

onConnected Method

• Added a check to close the existing channel before setting a new one.

onGoaway Method

• Modified to close the channel if it is still open before setting it to null.

Verifying this change

Checklist

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
33.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[AlbumenJ]

@icodening @EarthChen PTAL

[EarthChen]

LGTM