### 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`)
server/src/main/java/org/elasticsearch/transport/TransportService.java
final Transport.Connection connection,
        final String action,
        final TransportRequest request,
        final TransportRequestOptions options,
        final TransportResponseHandler<T> handler
    ) {
        try {
            final TransportResponseHandler<T> delegate;
            if (request.getParentTask().isSet()) {
                
                
                
                
                
                
                
                
                
                
                final Transport.Connection unwrappedConn = unwrapConnection(connection);
                final Releasable unregisterChildNode = taskManager.registerChildConnection(request.getParentTask().getId(), unwrappedConn);
                if (unregisterChildNode == null) {
                    delegate = handler;
                } else {
                    delegate = new UnregisterChildTransportResponseHandler<>(unregisterChildNode, handler, action);
                }
            } else {
                delegate = handler;
            }
            asyncSender.sendRequest(connection, action, request, options, delegate);