* support adding/removing clients from LBClient
* add/remove BalancingClient to be more flexible
* use RwMutex, lock for get
* lock mutex for init
* defer unlock for possible panic
* fix removing client
* fix filtering of slice
* fix removing references to removed items
Co-authored-by: Erik Dubbelboer <erik@dubbelboer.com>
Co-authored-by: Erik Dubbelboer <erik@dubbelboer.com>