[CI][Bugfix] Initialize _transfer_layer_group_ids in region_pull_worker fixture (#57211)

Signed-off-by: kimi-no-na-wa <kimi-no-na-wa@users.noreply.github.com>
Co-authored-by: kimi-no-na-wa <kimi-no-na-wa@users.noreply.github.com>
Co-authored-by: Robert Shaw <114415538+robertgshaw2-redhat@users.noreply.github.com>

tests/v1/kv_connector/unit/test_nixl_connector_hma.py

@@ -85,6 +85,7 @@ def region_pull_worker():
         remote_physical_blocks_per_logical=2,
     )
     worker.tp_mappings = {"P": TPMapping(((0,), (0,)), (0,), {0: 0}, 0)}
+    worker._transfer_layer_group_ids = ()
     worker._mixed_mem_types = True
     worker.src_xfer_handles_by_block_size = {64: 1}
     worker._dram_src_handles_by_block_size = {64: 2}