ipa-sam: fix gcc complaints on Rawhide
    
     In file included from /usr/include/string.h:519,
                      from /usr/include/lber.h:30,
                      from /usr/include/ldap.h:30,
                      from ipa_sam.c:12:
     In function 'strncpy',
         inlined from 'save_sid_to_secret' at ipa_sam.c:4478:2,
         inlined from 'pdb_init_ipasam' at ipa_sam.c:4985:12:
     /usr/include/bits/string_fortified.h:91:10: warning: 'strncpy' specified bound 255 equals destination size [-Wstringop-truncation]
        91 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
           |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    Fixes: https://pagure.io/freeipa/issue/8585
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>