sysctl: Fixes nsm_local_state bounds

Bound nsm_local_state sysctl writings between SYSCTL_ZERO
and SYSCTL_INT_MAX.

The proc_handler has thus been updated to proc_dointvec_minmax.

Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
[ cel: updated to handle zero - UINT_MAX instead ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>