recv request can only get maximum 1500 bytes payload in single response in
earlier design, this patch aggregrate more payloads（maximum 16k bytes）
into one response to make sure usrsock’s req/response mechanism is not
bottleneck during usrsock’s throughput test.
Signed-off-by: liangchaozhong <liangchaozhong@xiaomi.com>
d6070cdfc8