[data] fix env var for enabling resource reservation (#43793)

Fix the issue that the `RAY_DATA_ENABLE_OP_RESOURCE_RESERVATION` env var doesn't work. Because `bool("0")` returns `True`. 

---------

Signed-off-by: Hao Chen <chenh1024@gmail.com>

python/ray/data/context.py

@@ -3,7 +3,7 @@
 from typing import TYPE_CHECKING, Any, Dict, List, Optional, Union
 
 import ray
-from ray._private.ray_constants import env_integer
+from ray._private.ray_constants import env_bool, env_integer
 from ray.util.annotations import DeveloperAPI
 from ray.util.scheduling_strategies import SchedulingStrategyT
 
@@ -144,8 +144,8 @@
 DEFAULT_ACTOR_TASK_RETRY_ON_ERRORS = False
 
 # Whether to enable ReservationOpResourceAllocator by default.
-DEFAULT_ENABLE_OP_RESOURCE_RESERVATION = bool(
-    os.environ.get("RAY_DATA_ENABLE_OP_RESOURCE_RESERVATION", "1")
+DEFAULT_ENABLE_OP_RESOURCE_RESERVATION = env_bool(
+    "RAY_DATA_ENABLE_OP_RESOURCE_RESERVATION", True
 )
 
 # The default reservation ratio for ReservationOpResourceAllocator.