Fix VLLM_ASCEND_LLMDD_RPC_PORT renaming (#3108)

### What this PR does / why we need it?
This PR implements the renaming of the environment variable
VLLM_LLMDD_RPC_PORT to VLLM_ASCEND_LLMDD_RPC_PORT, as proposed and
tracked in
[#2450](https://github.com/vllm-project/vllm-ascend/pull/2450). The
renaming is intended to align the variable naming convention with other
Ascend-specific environment variables in the vllm-ascend codebase,
enhancing consistency and clarity for developers and users working with
Ascend-based deployments.

### Does this PR introduce _any_ user-facing change?
NA

### How was this patch tested?
CI passed with existing test.

- vLLM version: v0.10.2
- vLLM main:
9607d5eb44

Signed-off-by: wyu0-0 <woshilynn@163.com>

examples/offline_disaggregated_prefill_npu.py

@@ -79,7 +79,7 @@ def run_prefill(prefill_done, process_close):
 
 
 def run_decode(prefill_done):
-    os.environ['VLLM_LLMDD_RPC_PORT'] = '6634'
+    os.environ['VLLM_ASCEND_LLMDD_RPC_PORT'] = '6634'
     # ranktable.json needs be generated using gen_ranktable.sh
     # from the examples/disaggregated_prefill_v1 module in the main branch.
     os.environ['DISAGGREGATED_PREFILL_RANK_TABLE_PATH'] = "./ranktable.json"

tests/e2e/pd_disaggreate/run_edge_case_test.sh

@@ -70,7 +70,7 @@ run_tests_for_model() {
   # Start prefill instance
   PREFILL_PORT=8001
 
-  BASE_CMD="ASCEND_RT_VISIBLE_DEVICES=0 VLLM_LLMDD_RPC_PORT=5559 vllm serve $model_name \
+  BASE_CMD="ASCEND_RT_VISIBLE_DEVICES=0 VLLM_ASCEND_LLMDD_RPC_PORT=5559 vllm serve $model_name \
   --port $PREFILL_PORT \
   --seed 1024 \
   --enforce-eager \
@@ -90,7 +90,7 @@ run_tests_for_model() {
   DECODE_PORT=8002
 
   # Build the command with or without model-specific args
-  BASE_CMD="ASCEND_RT_VISIBLE_DEVICES=1 VLLM_LLMDD_RPC_PORT=6000 vllm serve $model_name \
+  BASE_CMD="ASCEND_RT_VISIBLE_DEVICES=1 VLLM_ASCEND_LLMDD_RPC_PORT=6000 vllm serve $model_name \
   --port $DECODE_PORT \
   --seed 1024 \
   --enforce-eager \