Fix pgbench's calculation of average latency, when -T is not used.

If the test duration was given in # of transactions (-t or no option),
rather as a duration (-T), the latency average was always printed as 0.
It has been broken ever since the display of latency average was added,
in 9.4.

Fabien Coelho

Discussion: <alpine.DEB.2.20.1607131015370.7486@sto>

src/bin/pgbench/pgbench.c

@@ -3296,9 +3296,11 @@ printResults(TState *threads, StatsData *total, instr_time total_time,
 	if (throttle_delay || progress || latency_limit)
 		printSimpleStats("latency", &total->latency);
 	else
-		/* only an average latency computed from the duration is available */
+	{
+		/* no measurement, show average latency computed from run time */
 		printf("latency average: %.3f ms\n",
-			   1000.0 * duration * nclients / total->cnt);
+			   1000.0 * time_include * nclients / total->cnt);
+	}
 
 	if (throttle_delay)
 	{