Cors with multiple origins returning error about moleculer-web

[felipegcampos]

Some additional information about cors + preflight + origin:

https://stackoverflow.com/questions/46086997/should-i-send-any-access-control-allow-origin-header-to-non-allowed-origins-in-t
https://stackoverflow.com/questions/42239643/when-does-firefox-set-the-origin-header-to-null-in-post-requests/42242802#42242802

Access-Control-Allow-Origin shouldn't be set if the prefligh or single request can't find the Origin within the request header. It should return 404 - Origin Not Found instead

I am adding it to my PR.

[icebob]

Thanks, please create a PR with fixes.

[felipegcampos]

Done, can you check pls? #44