perf bench: Add missing setlocale() call to allow usage of %'d style formatting

Without this we were not getting the thousands separator for big
numbers.

Noticed while developing 'perf bench uprobe', but the use of %' predates
that, for instance 'perf bench syscall' uses it.

Before:

  # perf bench uprobe all
  # Running uprobe/baseline benchmark...
  # Executed 1000 usleep(1000) calls
       Total time: 1054082243ns

   1054082.243000 nsecs/op

  #

After:

  # perf bench uprobe all
  # Running uprobe/baseline benchmark...
  # Executed 1,000 usleep(1000) calls
       Total time: 1,053,715,144ns

   1,053,715.144000 nsecs/op

  #

Fixes: c2a08203 ("perf bench: Add basic syscall benchmark")
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andre Fredette <anfredet@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Dave Tucker <datucker@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Derek Barbosa <debarbos@redhat.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/lkml/ZH3lcepZ4tBYr1jv@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>