The nng_aio_abort() function aborts an operation previously started
with the handle aio.
If the operation is aborted, then the callback
for the handle will be called, and the function
nng_aio_result() will return the error err.
This function does not wait for the operation to be fully aborted, but returns immediately.
If no operation is currently in progress (either because it has already finished, or no operation has been started yet), then this function has no effect.