Fix UnboundLocalError in explicit-cycledef path (parse COLDSTART_CYCS)

[ywangwof]

Summary

Fixes an UnboundLocalError that makes the explicit-cycledef path unusable for DA experiments.

When a user sets CYCLEDEF_* variables explicitly in the experiment file, smart_cycledefs() takes the explicit-override branch and never parses COLDSTART_CYCS into cold_cycs. The later da_nocold block — built whenever DO_JEDI=true (or DO_NONVAR_CLOUD_ANA=true) and COLDSTART_CYCS_DO_DA=false — references cold_cycs and raises:

UnboundLocalError: local variable 'cold_cycs' referenced before assignment
  File "workflow/rocoto_funcs/smart_cycledefs.py", line ~102, in smart_cycledefs
    exclude_cycs.extend(list(map(int, cold_cycs)))

That configuration (DA, skipping DA at the cold-start cycles) is common, so explicit cycledefs currently cannot be used with it.

Fix

Parse COLDSTART_CYCS in the explicit-override branch too, using the same default ('03 15') as the auto-compute branch, so da_nocold can exclude the cold-start cycles.

Impact

• Experiments using the auto-compute path (no CYCLEDEF_* set) never enter the modified branch → all existing XML output is unchanged.
• Experiments using explicit cycledefs with DA now generate correctly instead of crashing.

Reproducer / verification

Append to workflow/exp/exp.conus12km (which has DO_JEDI=true, COLDSTART_CYCS_DO_DA=false, COLDSTART_CYCS="00 12"):

export CYCLEDEF_IC="202405270000 202405270000 24:00:00"
export CYCLEDEF_LBC="202405270000 202405280000 12:00:00"
export CYCLEDEF_PROD="202405270000 202405270300 01:00:00"

• Before: ./setup_rocoto.py aborts with the UnboundLocalError above.
• After: generation succeeds and emits the expected da_nocold cycledef, e.g.:

<cycledef group="da_nocold" exclude_hours="0 12">202405270000 202405270300 01:00:00</cycledef>

py_compile clean.

[guoqing-noaa]

@ywangwof Thanks for fixing this! 👍
WE can safely remove comment lines 18-21. Thanks!