Wait until any currently‐executing job (or batch of jobs) on the queue with the specified id completes, then prevent any more jobs from being executed on that queue. Return 0 on success, and a non‐zero value if the queue is already paused or is being paused or deleted by another thread. Note that this method may be invoked from a job executing on the given queue, in which case this method does not wait. Note also that this method differs from disableQueue in that (1) pauseQueue stops processing for a queue, and (2) does not prevent additional jobs from being enqueued.