### Description

The `sendRequest` method is asynchronous and notifies a 
`TransportResponseHandler` when it completes the excecution
(successfully or unsuccessfully). 

When opening the connection we only catch `NodeNotConnectedException`
( https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/transport/TransportService.java#L719 ) which is currently fine as no implementations
throw other type of exception however, it'd be best to catch `Exception` here
so the `handler` gets notified of potential exceptions (as opposed to the caller
having to `try/catch` the call to `sendRequest`)
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
}
                    }
                };
            }
        };
        try (MockTransportService serviceC = buildService("TS_C", CURRENT_VERSION, null, Settings.EMPTY, true, true, interceptor)) {
            final CountDownLatch latch = new CountDownLatch(1);
            serviceC.connectToNode(
                serviceA.getLocalDiscoNode(),
                ConnectionProfile.buildDefaultConnectionProfile(Settings.EMPTY),
                new ActionListener<>() {
                    @Override
                    public void onResponse(final Releasable ignored) {
                        latch.countDown();
                    }
                    @Override
                    public void onFailure(final Exception e) {
                        fail(e.getMessage());
                    }
                }
            );
            latch.await();
            final AtomicReference<TransportException> te = new AtomicReference<>();
            final Transport.Connection connection = serviceC.getConnection(nodeA);
            serviceC.sendRequest(
                connection,
                "fail-to-send-action",
                TransportRequest.Empty.INSTANCE,
                TransportRequestOptions.EMPTY,
                new TransportResponseHandler.Empty() {