fix race on nc.bw assignment in kickFlusher()
fix race on nc.bw assignment in kickFlusher()

nats-io/nats,nats-io/go-nats,ZebinKang/go-nats,nats-io/go-nats,nats-io/nats,pires/nats,pires/nats,apcera/nats,wallyqs/go-nats,ZebinKang/go-nats,wallyqs/go-nats,apcera/nats