ncache: Fix sss_ncache_reset_permanent
    
    There was an off-by-one error in sss_ncache_reset_permanent that
    prevented the reset from working.
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    (cherry picked from commit d338bb46b8c03c33e6182e725911af6d778bcf00)