Docker compose validation allows both `networks` and `network_mode`

[pipex]

The following composition is rejected by docker-compose with service hello declares mutually exclusive network_modeandnetworks: invalid compose project

version: '2.4'

services: 
  hello:
    image: alpine
    command: ['sleep', 'infinity']
    networks: ['my-network']
    network_mode: host


networks:
  my-network:

While balena-compose allows it. Making the change might prevent invalid or ambiguous compositions reaching the supervisor