podman: Have writable access to root network configuration

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

meta-oniro-core/recipes-containers/podman/podman_%.bbappend

+# SPDX-FileCopyrightText: Huawei Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+inherit writables
+
+WRITABLES = "rootuser-netconfig"
+WRITABLE_PATH[rootuser-netconfig] = "/etc/cni/net.d"