Fix race condition on reading input in RESTEasy Reactive

[geoand]

The idea here is to ensure that Vert.x has not completed reading the input because we can install the proper listeners.
Without this change, the is a chance the input ends before we all the listeners thus resulting in an IllegalStateException being thrown.

Fixes: #15479

[stuartwdouglas]

I don't really see how this fixes it? If you are on a blocking thread then the pause() should be too late, while on an event loop thread pausing and resuming in the same method should have no effect?

[geoand]

I may be wrong, but what I was seeing is that pause ensured that we could add the listeners.
Without it, there was a chance that the request was ended before we add the listeners thus leading to an IllegalStateException being thrown.

Is there a more proper way to get around that problem in Vert.x?

[geoand]

After discussing (see https://quarkusio.zulipchat.com/#narrow/stream/187038-dev/topic/Resteasy.20Reactive/near/229432044), this fix should be OK for now, but we might need to come up with a more general solution in the future

[gsmet]

I will let @stuartwdouglas or @FroMage approve it and merge :).

[geoand]

Yup. OP also mentioned that he was going to test it, so let's see how that goes

[FroMage]

I saw the discussion and agree this is fine for now.

[FroMage]

So waiting for the test before we merge?

[geoand]

Let's give OP another half day :)