[Reviewer: Ellie] Initialize the cond var to use CLOCK_MONOTONIC

Ellie,

Please can you review my fix to initialize the cond var to use CLOCK_MONOTONIC - as it is, pop() calls always return immediately (because CLOCK_MONOTONIC times are always less than CLOCK_REALTIME).

Without this, on failure, we tight-loop if the SAS is unavailable.

Thanks,

Matt