[PATCH] oom: kthread infinite loop fix

Skip kernel threads, rather than having them return 0 from badness.
Theoretically, badness might truncate all results to 0, thus a kernel thread
might be picked first, causing an infinite loop.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>