[Bugfix] Fix speculative decode seeded test

[njhill]

This is a simpler fix for the bug explained in #6733 where we were not properly testing the per-request seeds int he spec decoding case, @tdoublep and I had fixed it at the same time.

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[tdoublep]

LGTM

Have confirmed that either of the following changes causes the test to fail:

diff --git a/vllm/spec_decode/spec_decode_worker.py b/vllm/spec_decode/spec_decode_worker.py
index 8cf0aa5b..17e54a31 100644
--- a/vllm/spec_decode/spec_decode_worker.py
+++ b/vllm/spec_decode/spec_decode_worker.py
@@ -598,11 +598,14 @@ class SpecDecodeWorker(LoraNotSupportedWorkerBase):
             # Get sequence group state
             generators = []
             for seq_group_metadata in seq_group_metadata_list:
+                '''
                 if (seq_group_metadata.state is not None
                         and seq_group_metadata.state.generator is not None):
                     generators.append(seq_group_metadata.state.generator)
                 else:
                     generators.append(None)
+                '''
+                generators.append(None)

or

diff --git a/vllm/spec_decode/batch_expansion.py b/vllm/spec_decode/batch_expansion.py
index 41f0aebf..df160134 100644
--- a/vllm/spec_decode/batch_expansion.py
+++ b/vllm/spec_decode/batch_expansion.py
@@ -293,6 +293,7 @@ class BatchExpansionTop1Scorer(SpeculativeScorer):
         for data in new_seq_data_dict.values():
             data.update_num_computed_tokens(data.get_len() - 1)
 
+        '''
         if (seq_group_metadata.state is not None
                 and seq_group_metadata.state.generator is not None):
             generator = torch.Generator(
@@ -301,6 +302,8 @@ class BatchExpansionTop1Scorer(SpeculativeScorer):
             state = SequenceGroupState(generator=generator)
         else:
             state = None
+        '''
+        state = None

This is not the case on main currently.