[NC-1772] Release DisconnectMessage to avoid leaking memory allocation. (#130)

Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

ethereum/p2p/src/main/java/tech/pegasys/pantheon/ethereum/p2p/netty/ApiHandler.java

@@ -92,6 +92,8 @@ final class ApiHandler extends SimpleChannelInboundHandler<MessageData> {
                 "Received Wire DISCONNECT, but unable to parse reason. Peer: {}",
                 connection.getPeer().getClientId(),
                 e);
+          } finally {
+            disconnect.release();
           }
 
           connection.terminateConnection(reason, true);