Change Pathways backend target from localhost to 127.0.0.1

This change uses the explicit IPv4 loopback address instead of the hostname "localhost" for the gRPC backend target, which could resolve to an IPv6 address.

PiperOrigin-RevId: 875382428

Author: guptaaka

pathwaysutils/experimental/shared_pathways_service/isc_pathways.py

@@ -28,7 +28,7 @@
 _JAX_PLATFORMS_KEY = "jax_platforms"
 _JAX_PLATFORM_PROXY = "proxy"
 _JAX_BACKEND_TARGET_KEY = "jax_backend_target"
-_JAX_BACKEND_TARGET_HOSTNAME = "grpc://localhost"
+_JAX_BACKEND_TARGET_HOSTNAME = "grpc://127.0.0.1"
 _DEFAULT_PROXY_IMAGE = "us-docker.pkg.dev/cloud-tpu-v2-images/pathways/proxy_server:latest"
 
 _logger = logging.getLogger(__name__)