perf tools: Do not zero sample_id_all for group members

Andi reported following malfunction:

  # perf record -e '{ref-cycles,cycles}:S' -a sleep 1
  # perf script
  non matching sample_id_all

That's because we disable sample_id_all bit for non-sampling group
members. We can't do that, because it needs to be the same over the
whole event list. This patch keeps it untouched again.

Reported-by: Andi Kleen <andi@firstfloor.org>
Tested-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180923150420.27327-1-jolsa@kernel.org


Fixes: e9add8ba ("perf evsel: Disable write_backward for leader sampling group events")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>