cpp/missing-check-scanf: False positive

https://github.com/ryao/zfs/security/code-scanning/420

https://github.com/ryao/zfs/blob/3881dd42bbfb7297f08e796c38b35d54e11ac500/lib/libspl/os/linux/gethostid.c#L50

CodeQL says `This variable is read, but may not have been written. It should be guarded by a check that the returns at least 1.`. However, that is already being done as part of `if (fscanf(f, "%lx", &hostid) != 1)`.