validation: add more test cases for linux_cgroups_network
validation: add more test cases for linux_cgroups_network

Test if network cgroups tests work correctly, with different test cases,
e.g. class ID, prio, interface name, whether net/user namespace is
enabled or not.

Signed-off-by: Dongsu Park <696fb7639d678a1e692fa501217d7509545d7331@kinvolk.io>

opencontainers/ocitools,opencontainers/ocitools,opencontainers/runtime-tools,opencontainers/runtime-tools