[Minor] Rename `ec_producer` field to `is_ec_producer` (#28884)

Signed-off-by: Nick Hill <nhill@redhat.com>

vllm/v1/engine/core.py

@@ -180,7 +180,7 @@ class EngineCore:
             logger.info("Batch queue is enabled with size %d", self.batch_queue_size)
             self.batch_queue = deque(maxlen=self.batch_queue_size)
 
-        self.ec_producer = (
+        self.is_ec_producer = (
             vllm_config.ec_transfer_config is not None
             and vllm_config.ec_transfer_config.is_ec_producer
         )
@@ -390,7 +390,7 @@ class EngineCore:
             exec_future = self.model_executor.execute_model(
                 scheduler_output, non_block=True
             )
-            if not self.ec_producer:
+            if not self.is_ec_producer:
                 model_executed = scheduler_output.total_num_scheduled_tokens > 0
 
             if self.is_pooling_model or not model_executed: