[users at bb.net] "could not rebuild: build still not finished"

[Dan Kegel]

On v0.8.11-pre-275-g1e72918...

grr.  I wanted to spam all my builders with identical repeats of a try
build (to verify same result on all builders),
but it wouldn't let me, it said "could not rebuild: build still not finished"

That message doesn't show up for non-try rebuilds, why should it show
up for try rebuilds?
/me scratches head.