[PATCH] sysctl: fix the selinux_sysctl_get_sid

I goofed and when reenabling the fine grained selinux labels for
sysctls and forgot to add the "/sys" prefix before consulting
the policy database.  When computing the same path using
proc_dir_entries we got the "/sys" for free as it was part
of the tree, but it isn't true for clt_table trees.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>