MC: Remove check if record is in the mapped address space
    
    There is a check in the memory cache code that checks if a record pointer
    points to the mmapped region . But since some time ago, we return not
    a pointer to the mmapped region itself, but a copy to avoid issues with
    invalidating an entry while the same entry is being returned.
    
    In most cases, the check is correct, simply because of how memory is laid
    out on Linux, but in some cases the check was failing and causing a high
    load of SSSD.
    
    Signed-off-by: Jakub Hrozek <jhrozek@redhat.com>
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/3776
    
    Reviewed-by: Michal Židek <mzidek@redhat.com>