lockd: avoid warning when CONFIG_SYSCTL undefined

When building without CONFIG_SYSCTL, the compiler saw an unused
label. This moves the label into the #ifdef it is used under.

fs/lockd/svc.c: In function ‘init_nlm’:
fs/lockd/svc.c:626:1: warning: label ‘err_sysctl’ defined but not used [-Wunused-label]

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>