fix: Use environment variable for SERVICE_ADDRESS.

Author: tjholm

nitric/config/default_settings.py

@@ -16,10 +16,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
+import os
 
 # Provides a set of default settings that env vars can replace
-
 # Nitric Membrane Service Address
-SERVICE_BIND = "127.0.0.1:50051"
-# Child Process (User Code) Host Address
-CHILD_ADDRESS = "127.0.0.1:8080"
+SERVICE_BIND = os.environ.get('SERVICE_ADDRESS', '127.0.0.1:50051');
+