Potential failure when detecting user activity.

[akheffache]

On this line,

OpenCue/rust/crates/rqd/src/system/nimby.rs

Line 327 in 22c9cd9

last_time.elapsed().unwrap_or(Duration::MAX) < self.idle_threshold

I think last_time.elapsed() could return Err if there is a problem with the clock (NTP issues, clock skew). In this case we will return always false. I think we should return TRUE in that case to make sure we are not taking over the machine.