Don't immediately delete KNSBackend, use deleteLater instead
While investigating a very strange looking backtrace, i came across this code which does seem to make sense, but which also seems like it might result in overly rapid deletes of some children that we might want to allow to do their thing for a little while yet.
I can't reproduce the bug below, but it seems like this might, possibly, in wildly crazy circumstances, maybe perhaps be the cause.