fix: Set TRTLLM_USE_UCX_KVCACHE=1 for reducing gpu mem usage

Signed-off-by: Jacky <[email protected]>

Author: kthui

tests/fault_tolerance/cancellation/test_trtllm.py

@@ -81,6 +81,7 @@ def __init__(self, request, mode: str = "prefill_and_decode"):
 
         # Set debug logging environment
         env = os.environ.copy()
+        env["TRTLLM_USE_UCX_KVCACHE"] = "1"
         env["DYN_LOG"] = "debug"
         env["DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUS"] = '["generate"]'
         env["DYN_SYSTEM_PORT"] = port