Instead of having custom code that basically duplicates the
functionality of `LoopControl.loop_for_fd` use that instead.
Additionally, the version used in the test had a bug where
it did not re-create the Loop device in the main loop when
it was close due to an error, leading errors in subsequent
usages of the device that would often manifest in CI runs:
fcntl.ioctl(self.fd, self.LOOP_SET_FD, fd)
ValueError: file descriptor cannot be a negative integer (-1)
280aca8f07