[P/D]Make kv-transfer env variable take effect & Fix load-balance proxy (#3981)

### What this PR does / why we need it?
Make kv-transfer env variable take effect and Fix load-balance proxy.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
By CI.


- vLLM version: v0.11.0
- vLLM main:
83f478bb19

---------

Signed-off-by: liziyu <liziyu16@huawei.com>
Signed-off-by: nwpu-zxr <zhouxuerong2@huawei.com>
Co-authored-by: liziyu <liziyu16@huawei.com>

vllm_ascend/distributed/utils.py

@@ -1,3 +1,5 @@
+import os
+
 import torch
 import torch.distributed as dist
 
@@ -45,3 +47,15 @@ def align_memory(tensor: torch.Tensor, alignment: int) -> torch.Tensor:
     aligned_addr = (data_ptr + alignment - 1) // alignment * alignment
     offset = (aligned_addr - data_ptr) // tensor.element_size()
     return tensor[int(offset):]
+
+
+def get_transfer_timeout_value():
+    ascend_transfer_timeout = os.getenv("ASCEND_TRANSFER_TIMEOUT", "")
+    if len(ascend_transfer_timeout) > 0:
+        return int(ascend_transfer_timeout)
+    hccl_rdma_timeout = int(os.getenv('HCCL_RDMA_TIMEOUT',
+                                      '20'))  # type: ignore
+    hccl_rdma_retry_cnt = int(os.getenv('HCCL_RDMA_RETRY_CNT',
+                                        '7'))  # type: ignore
+    return int((4.096 * (2**hccl_rdma_timeout)) * hccl_rdma_retry_cnt // 1000 +
+               3000)