Previously this test didn't handle well the case where there weren't any
connections to be closed, due to tacitly assuming that connections get opened
immediately.
Furthermore it wasn't straightforward to fix this as we were previously
depending on the non-immediate callback of untilAllInConnsRemoved to actually
wait for the unadvertise RPC to finish, rather than actually fencing on its
callback.
Previously this test didn't handle well the case where there weren't any connections to be closed, due to tacitly assuming that connections get opened immediately.
Furthermore it wasn't straightforward to fix this as we were previously depending on the non-immediate callback of untilAllInConnsRemoved to actually wait for the unadvertise RPC to finish, rather than actually fencing on its callback.
r @kriskowal @rf