Netty: Address TODO in NettyQuiesceListener

[pnicolucci]

https://github.com/OpenLiberty/open-liberty/blob/netty-transport-http/dev/io.openliberty.netty.internal.impl/src/io/openliberty/netty/internal/impl/NettyQuiesceListener.java

1. // TODO: Maybe we should check the map for the active channels if they have any connections left that could be better