uv adapter: reduce number of uv_poll_start calls

[noxiouz]

Internally uv_poll_start iterates over all attached event handlers to update event mask. It's quite expensive operation if there many event handlers attached to a loop

As redisLibuvEvents.events is a copy of what libuv should see, we can rely on it to avoid event mask updates.

For example, in async.c#L662 there is a high chance that fd is already being listened for writable events

Signed-off-by: Anton Tiurin [email protected]

[michael-grunder]

Hi @noxiouz sorry for the delay getting to this but I've been busy on another project.

I'll try to get this tested/merged this weekend.

[michael-grunder]

Closing in favor of rebased #1098