in a daemon all calls to the logger can throw an Interrupted exception,
which so far has silently stopped the curl thread without notifying its
transfers and leaving them stuck as a result. ensuring that the loggers
can never throw Interrupted will have very unpleasant side-effects, and
throwing depending on context requires large amount of bookkeeping. for
now it is easiest to abort all transfers on Interrupted during cleanup.
the test for this is extremely sketchy because we want to hit a single,
very specifically chosen, loger call in TransferItem::finish(). the bug
was triggered by the `act.progress` further down from what we're aiming
for, but that one is much harder to select for than the debug log here.
fixes#613
Change-Id: Id72efa64dd30cbbf256d2ab2a328457a0b095c6a
eldritch horrors
8c1ece93cc