test(hugegraph): fail closed on empty distributed FQDNs

[weicao]

Summary

Child PR into dev/hugegraph-release-1.0.

PD, Store, and Server start scripts already refuse an empty or comma-only podFQDNs list. Add offline tests so a missing Raft peer list cannot be treated as count 0.

Test

bash addons/hugegraph/tests/start_pd_test.sh
bash addons/hugegraph/tests/start_store_test.sh
bash addons/hugegraph/tests/start_server_test.sh
bash addons/hugegraph/tests/contract_test.sh
HugeGraph addon offline contracts passed

Main PR: #3412

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (c986b81) to head (64d4e89).

Additional details and impacted files

@@                    Coverage Diff                    @@
##           dev/hugegraph-release-1.0   #3423   +/-   ##
=========================================================
  Coverage                       0.00%   0.00%           
=========================================================
  Files                             69      69           
  Lines                           7275    7275           
=========================================================
  Misses                          7275    7275           

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