src/hooks/dhcp/high_availability/ha_service.cc

    HAService
        clientConnectHandler() - new client connection connect callback
        clientCloseHandler() - new client connection close callback

        asyncSendLeaseUpdate()
        asyncSendHeartbeat()
        asyncDisableDHCPService()
        asyncEnableDHCPService()
        asyncSyncLeasesInternal() - added new call backs to
        HttpClient::asyncSendRequest() invocation

src/lib/http/client.cc
    Connection::resetState() - added reset of close callback