perf: fix temporary file ownership check

perf: fix temporary file ownership check

A file in /tmp/ might be a symlink, so lstat() should be used instead of
stat().

Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20110811205537.GA22864@albatros
Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>