[sysctl] Fix breakage on systems with older glibc

As predicted during code review, the sysctl(2) changes made systems with
old glibc nearly unusable.  About every command gives a:

  warning: process `ls' used the deprecated sysctl system call with 1.4

warning in the log.

I see this on a SUSE 10.0 system with glibc 2.3.5.

Don't warn for this common case.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>