Load active modules when onboarding

[tyxla]

This PR allows active modules to be loaded while onboarding. We need to handle this special case because we might be in a state where we're not connected and not in development mode in the same time, but we still need to load the active modules.

Fixes Automattic/wp-calypso#21930

To test:

1. Create a fresh Jurassic Ninja site.
2. Install JP beta, switch on bleeding edge.
3. SSH into the JN site and apply this branch manually.
4. Go to https://JNsite.com/wp-admin/admin.php?page=jetpack&action=onboard where JNsite.com is a fresh Jurassic Ninja site.
5. On the site type step, select Business.
6. On the Business address step, input your business address and submit the step.
7. Go to wp-admin and verify that the contact info widget is active and is properly inserted in your sidebar with all the business address inside.

[ockham]

Works perfectly 👍

[ockham]

Also tested on my JP sandbox. Works great there, too!

[dereksmart]

Tests well!