Use net=none for gnocchi_init_lib

Similar to Id3e60de7bb5a13e32544bed76e4970d53a9257d4 we need to
use net: none here with podman explicitly otherwise it attempts
(and fails) to connect to the local network.

Change-Id: Icc2b3e2d626e25b3a6d16205e5348a806a3276ce
Closes-bug: #1815650

docker/services/gnocchi-api.yaml

@@ -166,6 +166,7 @@ outputs:
             command: ['/bin/bash', '-c', 'chown -R gnocchi:gnocchi /var/log/gnocchi']
           gnocchi_init_lib:
             image: *gnocchi_api_image
+            net: none
             user: root
             volumes:
               - str_replace: