Review Board 4 introduced a regression when confirming trust in

repository certificates or SSH keys. While this isn't used particularly

often (as most people now interface with services like GitHub or with

repositories that don't require this kind of verification), it has been

noticed recently by a couple different parties.
The problem was that, when clicking "I trust this host," blank form data

was being sent along. This happened because the fields on the form are

disabled when this prompt is shown, and disabled fields aren't sent in

form data.
We had code meant to deal with this. It re-enabled the disabled fields

when confirming. However, a restyle removed the old class name on the

alert, preventing this from working.
This change simply adds back the old class name, allowing this to work

again. We're not worrying about modern naming at this stage, since the

whole form is being rewritten for Review Board 6.

Triggered a host verification prompt. Verified that the form fields

were no longer disabled and the form data was properly sent along.