RSocketDslTests: Resolve server port eagerly

Looks like there is some connection race condition in Netty on Linux,
so we may not be started on server side fully when we try to select a
port from the OS

* Move local port resolution and, therefore, RSocket server start into
the earlier phase before creating a client

spring-integration-rsocket/src/test/java/org/springframework/integration/rsocket/dsl/RSocketDslTests.java

@@ -40,13 +40,9 @@
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 
 import io.netty.buffer.PooledByteBufAllocator;
-import io.netty.util.NetUtil;
 import io.rsocket.frame.decoder.PayloadDecoder;
-import io.rsocket.transport.netty.client.TcpClientTransport;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
-import reactor.netty.tcp.InetSocketAddressUtil;
-import reactor.netty.tcp.TcpClient;
 
 /**
  * @author Artem Bilan
@@ -87,18 +83,10 @@ public ServerRSocketConnector serverRSocketConnector() {
 			return serverRSocketConnector;
 		}
 
-
 		@Bean
 		public ClientRSocketConnector clientRSocketConnector(ServerRSocketConnector serverRSocketConnector) {
-			ClientRSocketConnector clientRSocketConnector =
-					new ClientRSocketConnector(
-							TcpClientTransport.create(
-									TcpClient.create()
-											.addressSupplier(() ->
-													InetSocketAddressUtil.createUnresolved(
-															NetUtil.LOCALHOST.getHostAddress(),
-															serverRSocketConnector.getBoundPort().block()))
-							));
+			int port = serverRSocketConnector.getBoundPort().block();
+			ClientRSocketConnector clientRSocketConnector = new ClientRSocketConnector("localhost", port);
 			clientRSocketConnector.setFactoryConfigurer((factory) -> factory.frameDecoder(PayloadDecoder.ZERO_COPY));
 			clientRSocketConnector.setRSocketStrategies(rsocketStrategies());
 			clientRSocketConnector.setAutoStartup(false);