cam - errors in severe/radar verification

[PerryShafran-NOAA]

In testing PR #682 to change KEEPDATA to NO, it was noticed in testing of severe and radar prep and stats jobs that there were some errors and warnings that need to be addressed. Examples here:

In jevs_cam_severe_prep, the following warning occurred:

jevs_cam_severe_prep.o19257940:WARNING: 
jevs_cam_severe_prep.o19257940:WARNING: Zero observations retained!
jevs_cam_severe_prep.o19257940:WARNING: 

In several of the severe stats jobs, the following warnings existed:

echo 'WARNING: Missing file is /lfs/h2/emc/vpppg/noscrub/emc.vpppg/evs/v2.0/prep/cam/nam.20250310/namnest.t12z.MXUPHL25_A24.SSPF.2025031112-2025031212.f48.nc\n'

WARNING: 
WARNING: process_scores() -> Forecast and observation valid times do not match (20250312_120000 != 19700101_000000) for Prob_MXUPHL25_A24_geHWT(*,*) versus Fscale_mask(*,*).
WARNING: 

The above warnings were also seen in the href severe stats job, but also this error:

WARNING: 
WARNING: read_data_plane() -> Prob_MXUPHL25_A24_geHWT(*,*) not found in forecast file: /lfs/h2/emc/vpppg/noscrub/emc.vpppg/evs/v2.0/prep/cam/href.20250311/href.t00z.MXUPHL25_A24.SSPF.2025031112-2025031212.f36.nc
WARNING: 
ERROR  : 
ERROR  : process_scores() -> no requested data found!  Exiting...
ERROR  : 

A FATAL ERROR followed after that.

See the log files for prep here: /lfs/h2/emc/vpppg/noscrub/alicia.bentley/pr682test/EVS/dev/drivers/scripts/prep/cam
See the log files for stats here: /lfs/h2/emc/vpppg/noscrub/alicia.bentley/pr682test/EVS/dev/drivers/scripts/stats/cam

All these issues should be resolved for both the RRFS branch (in case these errors are found there as well) as well as the develop branch.