When latency-monitor-threshold is set to 0, it means the latency monitor
is disabled, and in VM_LatencyAddSample, we wrote the condition
incorrectly, causing us to record latency when latency was turned off.
This bug was introduced in the very first day, see e3b1d6d, it was merged
in 2019.
Signed-off-by: Binbin <binloveplay1314@qq.com>