`FATES_C13DISC_SZPF` not passing restart

[glemieux]

During the update of the FatesColdAllVars testmod (via ESCOMP/CTSM#2936), I realized that some variables were missing and ran the FindInactive.py tool to update the list. During regression testing I discovered that history output FATES_C13DISC_SZPF is failing COMPARE_base_rest. All other variables within the test mod are b4b.

[glemieux]

This is a duplicate of #700.