restrict refresh ring to heartBeat (apache#1015)

* don't trace unless query is trace enabled

When 'nodetool settraceprobability' is used,
it's possible to get a response with trace information
even though client did not specifically mark the query
for tracing.

* added myself as an author

* restrict refresh ring to heartBeat

GetHosts uses queries on control connection. Any query error will
cause reconnection and refresh ring which calls GetHosts and thus
deadlocks.

Also it seems neater to have the ring refresh be done only by heartBeat.

Fixes apache#928

control.go

@@ -381,7 +381,7 @@ func (c *controlConn) HandleError(conn *Conn, err error, closed bool) {
 		return
 	}
 
-	c.reconnect(true)
+	c.reconnect(false)
 }
 
 func (c *controlConn) getConn() *connHost {