Harmonize uses of fgets()

fgets() already takes care of reading at most size-1 characters.

This patch corrects all

    fgets(buf, CF_BUFSIZE - 1, fd);
    fgets(buf, CF_BUFSIZE, fd);

to

    fgets(buf, sizeof(buf), fd);

Such usage of fgets() was already used in sysinfo.c:1532

This improves readability, tracking the type of the buffer is no longer needed, and if its type change its size will follow.