TESTS: Set SO_LINGER = 0 for MockNioTransport (#32560)

* TESTS: Set SO_LINGER = 0 for MockNioTransport

* Prevents lingering sockets in TIME_WAIT piling up during test runs and leading to port collisions that manifest as timeouts
* Fixes #32552

test/framework/src/main/java/org/elasticsearch/transport/MockTcpTransport.java

@@ -182,6 +182,7 @@ public class MockTcpTransport extends TcpTransport {
         executor.submit(() -> {
             try {
                 socket.connect(address);
+                socket.setSoLinger(false, 0);
                 channel.loopRead(executor);
                 connectListener.onResponse(null);
             } catch (Exception ex) {

test/framework/src/main/java/org/elasticsearch/transport/nio/MockNioTransport.java

@@ -193,6 +193,7 @@ public class MockNioTransport extends TcpTransport {
             BytesChannelContext context = new BytesChannelContext(nioChannel, selector, (e) -> exceptionCaught(nioChannel, e),
                 readWriteHandler, new InboundChannelBuffer(pageSupplier));
             nioChannel.setContext(context);
+            nioChannel.setSoLinger(0);
             return nioChannel;
         }