Fix NullPointer when message shortcircuited (#55945)

Currently if we shortcircuit a message the breaker release is null since
there is nothing to be broken. However, the TcpTransportChannel
infrastructure still expects it. This commit resolves this issue be
returning a no-op breaker release.

server/src/main/java/org/elasticsearch/transport/InboundMessage.java

@@ -87,7 +87,11 @@ public class InboundMessage implements Releasable {
     public Releasable takeBreakerReleaseControl() {
         final Releasable toReturn = breakerRelease;
         breakerRelease = null;
-        return toReturn;
+        if (toReturn != null) {
+            return toReturn;
+        } else {
+            return () -> {};
+        }
     }
 
     public StreamInput openOrGetStreamInput() throws IOException {

server/src/test/java/org/elasticsearch/transport/InboundAggregatorTests.java

@@ -130,6 +130,7 @@ public class InboundAggregatorTests extends ESTestCase {
         assertThat(aggregated, notNullValue());
         assertTrue(aggregated.isShortCircuit());
         assertThat(aggregated.getException(), instanceOf(ActionNotFoundTransportException.class));
+        assertNotNull(aggregated.takeBreakerReleaseControl());
     }
 
     public void testCircuitBreak() throws IOException {