add: optional overrides for command/args of Netbox container

[connor-snapdocs]

quick change to enable the override of the image's entrypoint. Enables some run-time modification of the default image without having to create a fork of it.

[jswny]

LGTM!

[nataliest]

git rebase -i HEAD~3 ? lgtm!

[RangerRick]

@connor-snapdocs this seems reasonable, mind rebasing it so we can let it run through the test framework and to match the new layout? Thanks!