Reduce buffer size when proxying

closes codecentric#713

Author: joshiste

spring-boot-admin-server/src/main/java/de/codecentric/boot/admin/server/web/servlet/InstancesProxyController.java

@@ -84,7 +84,7 @@ public Mono<Void> endpointProxy(@PathVariable("instanceId") String instanceId,
  //otherwise the FrameworkServlet will add wrong Allow header for OPTIONS request
  ClientResponse clientResponse = super.forward(instanceId, uri, request.getMethod(), request.getHeaders(),
  () -> BodyInserters.fromDataBuffers(
- DataBufferUtils.readInputStream(request::getBody, this.bufferFactory, 16384))).block();
+ DataBufferUtils.readInputStream(request::getBody, this.bufferFactory, 4096))).block();
 
  response.setStatusCode(clientResponse.statusCode());
  response.getHeaders().addAll(filterHeaders(clientResponse.headers().asHttpHeaders()));