Sukadev reported segfault on releasing perf env's numa data.  It's due
to nr_numa_nodes being set no matter if the numa data gets parsed
properly. The perf_env__exit crash the on releasing non existed data.

Setting nr_numa_nodes only when data are parsed out properly.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Reported-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-dt9c0zgkt4hybn2cr4xiawta@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>