Optimize common use patterns.

Most calls to stats-job are for a job currently reserved by the
caller, so check that first before doing a (slow) sequential scan
through the lists of ready and delayed jobs.

prot.c

@@ -589,9 +589,9 @@ peek_ready_job(unsigned long long int id)
 static job
 peek_job(unsigned long long int id)
 {
- return peek_ready_job(id) ? :
+ return find_reserved_job(id) ? :
+ peek_ready_job(id) ? :
  pq_find(&delay_q, id) ? :
- find_reserved_job(id) ? :
  find_buried_job(id);
 }