Client Close events are not properly connected to pool release

[smaldini]

As reported in cloudfoundry/cf-java-client#857, the client pooled context does not seem to bridge closeFuture correctly.

The core issue being that https://github.com/reactor/reactor-netty/blob/master/src/main/java/reactor/ipc/netty/channel/PooledClientContextHandler.java#L200 is never true since the channel handler is created before by doPipeline. That means we never attach closeFuture(release(ch)).