perf trace: Do not show the runtime_ms for a thread when not collecting it

That field is only updated when we use the "sched:sched_stat_runtime"
tracepoint, and that is only done so far when we use the '--stat' command line
option, without it we get just zeros, confusing the users:

Without this patch:

# trace -a -s sleep 1
<SNIP>
qemu-system-x86 (9931), 468 events, 9.6%, 0.000 msec

syscall calls total min avg max stddev
(msec) (msec) (msec) (msec) (%)
---------- ------ --------- --------- --------- --------- ------
ppoll 98 982.374 0.000 10.024 29.983 12.65%
write 34 0.401 0.005 0.012 0.027 5.49%
ioctl 102 0.347 0.002 0.003 0.007 3.08%

firefox (10871), 1856 events, 38.2%, 0.000 msec

(msec) (msec) (msec) (msec) (%)
---------- ------ --------- --------- --------- --------- ------
poll 395 934.873 0.000 2.367 17.120 11.51%
recvmsg 395 0.988 0.001 0.003 0.021 4.20%
read 106 0.460 0.002 0.004 0.007 3.17%
futex 24 0.108 0.001 0.004 0.010 10.05%
mmap 2 0.041 0.016 0.021 0.026 23.92%
write 6 0.027 0.004 0.004 0.005 2.52%

After this patch that ', 0.000 msecs' gets suppressed when --stat is not
in use.

Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Milian Wolff <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-trace.c

···
 		printed += fprintf(fp, ", %lu majfaults", ttrace->pfmaj);
 	if (ttrace->pfmin)
 		printed += fprintf(fp, ", %lu minfaults", ttrace->pfmin);
-	printed += fprintf(fp, ", %.3f msec\n", ttrace->runtime_ms);
+	if (trace->sched)
+		printed += fprintf(fp, ", %.3f msec\n", ttrace->runtime_ms);
+	else if (fputc('\n', fp) != EOF)
+		++printed;
+
 	printed += thread__dump_stats(ttrace, trace, fp);
 
 	return printed;