KCM: be aware that size_t might have different size than other integers
The memory assignment for the size_t type might be larger on some
platforms than for 32bit integer values and even for value of unsigned
int type. When converting/casting size_t to those values special care
has to be taken especially when pointers to those values are used.
The patch also contains a fix for a unit test which now should detect
the issue properly.
Related to https://pagure.io/SSSD/sssd/issue/3757
Reviewed-by: Fabiano FidĂȘncio <fidencio@redhat.com>