perf bench: Set more defaults in the 'numa' suite

Currently,

  $ perf bench numa mem

errors out with usage information. To make this more user-friendly, let
us provide a minimum set of default values required for a test
run. As an added bonus,

  $ perf bench all

now goes all the way to completion.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1395964219-22173-2-git-send-email-artagnon@gmail.com
Signed-off-by: Jiri Olsa <jolsa@redhat.com>