Create Bootstrap with unresolved address

This forces the Netty client use InetAddress.getByName/getAllByName for each
connect() request, which will delegate to the JVM's DNS lookup and caching
mechanism

Author: dagnir

.changes/next-release/bugfix-NettyNIOHTTPClient-f222168.json

@@ -0,0 +1,5 @@
+{
+    "type": "bugfix",
+    "category": "Netty NIO HTTP Client",
+    "description": "Fix issue where DNS resolution for a host is only made once for the initial request to the host. If the DNS entries change for a hostname, the client will resolve the new address until the client is closed and recreated."
+}

http-clients/netty-nio-client/src/main/java/software/amazon/awssdk/http/nio/netty/internal/AwaitCloseChannelPoolMap.java

@@ -178,7 +178,7 @@ private Bootstrap createBootstrap(URI poolKey) {
                         .channelFactory(sdkEventLoopGroup.channelFactory())
                         .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, configuration.connectTimeoutMillis())
                         // TODO run some performance tests with and without this.
-                        .remoteAddress(new InetSocketAddress(host, port));
+                        .remoteAddress(InetSocketAddress.createUnresolved(host, port));
         sdkChannelOptions.channelOptions().forEach(bootstrap::option);
 
         return bootstrap;