Fix snprintf size argument

[ggalgoczi]

Fix snprintf size argument in sdigest.h to avoid _FORTIFY_SOURCE abort caused by glibc hardening feature.

[ggalgoczi]

sdigest::Finalize() and sdigest::DescRaw() call snprintf:

• Larger size argument is given than the allocated length
• Never ran over the allocated length so there was no problem due to this ever
• However eic_cuda container uses _FORTIFY_SOURCE, a compile-time/runtime hardening feature in glibc that aborts