fix: keep writing previous speedtest result (#15484)
fix: keep writing previous speedtest result (#15484)

when object speedtest is running keep writing
previous speedtest result back to client until
we have a new result - this avoids sending back
blank entries in between the speedtest when it
is running in 'autotune' mode.
minio/minio,krisis/minio,krisis/minio,donatello/minio,vadmeste/minio,donatello/minio,minio/minio,vadmeste/minio,balamurugana/minio,balamurugana/minio