Consume all params and content on extension Rest Request exception (o…

…pensearch-project#8096)

Signed-off-by: Daniel Widdis <widdis@gmail.com>

server/src/main/java/org/opensearch/rest/extensions/RestSendToExtensionAction.java

@@ -219,6 +219,10 @@ public void handleResponse(RestExecuteOnExtensionResponse response) {
             @Override
             public void handleException(TransportException exp) {
                 logger.debug("REST request failed", exp);
+                // On failure the original request params and content aren't consumed
+                // which gives misleading error messages, so we just consume them here
+                request.params().keySet().stream().forEach(p -> request.param(p));
+                request.content();
                 inProgressFuture.completeExceptionally(exp);
             }