Adjusted based on comments
Adjusted based on comments

* Disable Client Ping with a PingInterval <= 0
* Don't bother nil'ing out the timer
* comment: sendPing requires a lock
* switch bw.Flush() to kickFlusher when sending a PING

wallyqs/nats,apcera/nats,pires/nats,gale320/nats,nats-io/nats,wallyqs/go-nats,ZebinKang/go-nats,Lanzafame/nats,apcera/nats,chzyer-dev/nats,aforward/nats,nats-io/go-nats,dnascimento/nats,nats-io/nats,wallyqs/go-nats,nats-io/go-nats,pires/nats,ZebinKang/go-nats,the-control-group/nats,dnascimento/nats,the-control-group/nats