Fix bug causing start->options to be ignored when network was set to false

[PauloMigAlmeida]

When the network->enable toggle mechanism was implemented, I forgot to handle an edge case that I just realized today.

It causes some of the options on the start->options to be ignored when network->enable == false given the way that the function _get_network_commands used to work. This PR fixes this behaviour.

Example config:

agent:
  build:
    context: .
    recipe: ./recipes/corecli/main.def
    options:
      - fakeroot
  start:
    options:
      - containall
  network:
    enable: false
  volumes:
    - ./volumes/corecli/logs:/app_logs
  depends_on:
    - apollo

Before:

$ singularity-compose -f singularity-compose-local.yml --debug up

Creating agent
DEBUG singularity instance start \
    --bind <redacted>/volumes/corecli/logs:/app_logs \
    --bind <redacted>/resolv.conf:/etc/resolv.conf \
    --bind <redacted>/etc.hosts:/etc/hosts \
    --hostname agent \
    --writable-tmpfs \
    <redacted>/agent.sif agent 

After:

$ singularity-compose -f singularity-compose-local.yml --debug up

Creating agent
DEBUG singularity instance start \
    --bind <redacted>/volumes/corecli/logs:/app_logs \
    --bind <redacted>/resolv.conf:/etc/resolv.conf \
    --bind <redacted>/etc.hosts:/etc/hosts \
    --containall
    --hostname agent \
    --writable-tmpfs \
    <redacted>/agent.sif agent 

[vsoch]

This looks good, and I like moving the addition of start_opts down into the root of creation instead of the function to get start options.

[vsoch]

Thank you!

https://pypi.org/project/singularity-compose/0.1.15/