test: use aux file v2 policy by default

Signed-off-by: Alex Chi Z <chi@neon.tech>

test_runner/fixtures/neon_fixtures.py

@@ -1604,7 +1604,7 @@ def create_tenant(
         shard_stripe_size: Optional[int] = None,
         placement_policy: Optional[str] = None,
         set_default: bool = False,
-        aux_file_v2: Optional[AuxFileStore] = None,
+        aux_file_policy: Optional[AuxFileStore] = None,
     ) -> Tuple[TenantId, TimelineId]:
         """
         Creates a new tenant, returns its id and its initial timeline's id.
@@ -1629,14 +1629,15 @@ def create_tenant(
                 )
             )
 
-        if aux_file_v2 is AuxFileStore.V2:
+        if aux_file_policy is AuxFileStore.V2:
             args.extend(["-c", "switch_aux_file_policy:v2"])
-
-        if aux_file_v2 is AuxFileStore.V1:
+        elif aux_file_policy is AuxFileStore.V1:
             args.extend(["-c", "switch_aux_file_policy:v1"])
-
-        if aux_file_v2 is AuxFileStore.CrossValidation:
+        elif aux_file_policy is AuxFileStore.CrossValidation:
             args.extend(["-c", "switch_aux_file_policy:cross-validation"])
+        else:
+            # use aux file v2 if the policy is not specified
+            args.extend(["-c", "switch_aux_file_policy:v2"])
 
         if set_default:
             args.append("--set-default")