Fix missing ResourceLeak.close() in AbstractDnsMessage

Motivation:

ResourceLeak.close() must be called when a reference-counted resource is
deallocated, but AbstractDnsMessage.deallocate() forgot to call it.

Modifications:

Call ResourceLeak.close() for the tracked AbstractDnsMessage instances

Result:

Fix the false resource leak warnings

codec-dns/src/main/java/io/netty/handler/codec/dns/AbstractDnsMessage.java

@@ -375,6 +375,11 @@ public DnsMessage retain(int increment) {
     @Override
     protected void deallocate() {
         clear();
+
+        final ResourceLeak leak = this.leak;
+        if (leak != null) {
+            leak.close();
+        }
     }
 
     @Override