The refactoring in #980 changed to having only one instance of the async
req (like on Unix), so like on Unix, we also need to drain the queue of
all pending messages when we make the callback pending.
Fixes: https://github.com/libuv/libuv/pull/1951
PR-URL: https://github.com/libuv/libuv/pull/1960
Co-authored-by: Jameson Nash <vtjnash@gmail.com>
Reviewed-By: Jameson Nash <vtjnash@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
