bugfix oidc client not working

the file gets created, but you need to wait some time to get data into it

docker/devicehub.entrypoint.sh

@@ -119,18 +119,21 @@ config_oidc() {
 
                 # in DEVICEHUB_HOST we remove anything before ://
                 client_id_config="/shared/client_id_${DEVICEHUB_HOST#*://}"
+                client_id=
+                client_secret=
 
                 # wait that the file generated by the server_id is readable
                 while true; do
                         if [ -f "${client_id_config}" ]; then
-                                break
+                                client_id="$(cat "${client_id_config}" | jq -r '.client_id')"
+                                client_secret="$(cat "${client_id_config}" | jq -r '.client_secret')"
+                                if [ "${client_id}" ] && [ "${client_secret}" ]; then
+                                        break
+                                fi
                         fi
                         sleep 1
                 done
 
-                client_id="$(cat "${client_id_config}" | jq -r '.client_id')"
-                client_secret="$(cat "${client_id_config}" | jq -r '.client_secret')"
-
                 flask add_client_oidc \
                       "${SERVER_ID_HOST}" \
                       "${client_id}" \