Use getattr to get an accurate link count when needed.  This is cheaper and
more accurate than trying to derive it by walking the thread list of a
process.

Especially as it happens when needed stat instead of at readdir time.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>