perf bench numa: Fix immediate meeting of convergence condition

This patch fixes the race in the beginning of benchmark run when some
threads hasn't got assigned curr_cpu yet so they don't occur in
nodes-of-process stats and benchmark concludes that all remaining
threads are converged already.

The race can be reproduced with small amount of threads and some bigger
amount of shared process memory, e.g. one process, two threads and 5GB
of process memory.

Signed-off-by: Petr Holasek <pholasek@redhat.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1429198699-25039-4-git-send-email-pholasek@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>