fix: cache warmup as www-data in Dockerfile

Dockerfile

@@ -34,6 +34,7 @@ RUN mkdir -p var/cache var/log public/uploads \
     && chmod -R 775 var
 
 ENV APP_ENV=prod APP_DEBUG=0
+USER www-data
 RUN APP_SECRET=build-placeholder \
     DATABASE_URL="postgresql://build:build@127.0.0.1:5432/build" \
     DATABASE_CABINET_URL="postgresql://build:build@127.0.0.1:5432/build" \
@@ -41,6 +42,5 @@ RUN APP_SECRET=build-placeholder \
     REDIS_URL="redis://127.0.0.1:6379" \
     php bin/console cache:warmup --env=prod || true
 
-USER www-data
 EXPOSE 9000
 CMD ["php-fpm", "-F"]