VHOST: Prompt users to restart app for debugging

[krallin]

When a VHOST fails to provision, it can be attempted again by running an aptible restart (or re-deploying the app). Since there's a user behind the screen in those cases, it's an occasion for us to show debugging output and explain what went wrong.

As of https://github.com/aptible/sweetness/pull/648, we'll start doing so for VHOSTs, by explaining the most common error case, i.e. the container does not EXPOSE any ports. This patch updates the VHOST error message accordingly and invites users to retry via a restart rather than contact support directly (which should help resolve their issue faster).

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cc @fancyremarker @blakepettersson @sandersonet

[krallin]

Looks like this in the UI:

[fancyremarker]

💯 , this will be very helfpul.