fixes LoadbalanceTest issues

[rstoyanchev]

I think, on occasion, not all requests had finished executing when the counter is checked.

[rstoyanchev]

It looks like some requests are failing like this:

2021-02-18T11:23:19.6328178Z STD_ERR: java.lang.ClassCastException: class io.rsocket.loadbalance.PooledRSocket cannot be cast to class io.rsocket.loadbalance.WeightedStats (io.rsocket.loadbalance.PooledRSocket and io.rsocket.loadbalance.WeightedStats are in unnamed module of loader 'app')
2021-02-18T11:23:19.6332679Z STD_ERR: 	at io.rsocket.loadbalance.LoadbalanceTest.lambda$shouldDeliverAllTheRequestsWithWeightedStrategy$7(LoadbalanceTest.java:109)
2021-02-18T11:23:19.6336141Z STD_ERR: 	at io.rsocket.loadbalance.WeightedLoadbalanceStrategy.select(WeightedLoadbalanceStrategy.java:72)
2021-02-18T11:23:19.6338775Z STD_ERR: 	at io.rsocket.loadbalance.RSocketPool.doSelect(RSocketPool.java:217)

The test sets up a weightedStatsResolver that simply downcasts the RSocket which is PooledRSocket. So when there are two loadbalance targets, and RSocketPool needs to make a choice, it fails.

[rstoyanchev]

I've pushed an update that should address the issue.

[rstoyanchev]

I undid the CountDownLatch and force pushed in order to see the actual change that remains. Basically fixing a ClassCastException from the weightedStatsResolver.

[OlegDokuka]

LGTM