Make ChannelOperations.DisposedChannel#close non operational (#3592)

DisposedChannel is effective when request/response is terminated and replaces the actual channel.
At that point ChannelOperations.DisposedChannel#close must be non operational.

Fixes #3591

reactor-netty-core/src/main/java/reactor/netty/channel/ChannelOperations.java

@@ -709,6 +709,17 @@ static final class DisposedChannel extends AbstractChannel {
 			this.remoteAddress = actual.remoteAddress();
 		}
 
+		@Override
+		public ChannelFuture close() {
+			return newSucceededFuture();
+		}
+
+		@Override
+		public ChannelFuture close(ChannelPromise promise) {
+			promise.setSuccess();
+			return promise;
+		}
+
 		@Override
 		public ChannelFuture closeFuture() {
 			return newSucceededFuture();