Review of #276: a move deleted before it published, so a failed publish
lost an ask; a verb's own process ran a pass beside the serving one, so
one could resume the queue while the other moved asks and a build ran
twice. The copy is now published first and second copies removed by id,
asks only signal the acting controller's loop, moves stop with 5 s of
the pause left, a cancel finds a moved ask by id, and an unreadable ask
keeps its age.
A merged change's walk waited minutes on its build behind checks in a
first-come queue. The queue now hands deliveries out first, a check that
has waited ten minutes before deliveries asked after it, and says each
ask's kind; the order is kept in the work queue itself.
jschoubben