fix(installWizard): Fix client default values not set

[BYK]

Fixes #12813.

Just checked the payload to the server after the fix, it is now as follows w/ onpremise:

{
    "auth.allow-registration": false,
    "beacon.anonymous": false,
    "mail.from": "root@localhost",
    "mail.password": "lol really",
    "mail.port": 25,
    "mail.use-tls": false,
    "mail.username": "root",
    "system.admin-email": "ben@byk.im",
    "system.url-prefix": "http://localhost:9000"
}

This also indeed fixes the empty DSN issue.

[dcramer]

I will trust your tests on this. The forms/options behavior here was super problematic to work around. I think we should talk with @billyvg / @lynnagara about removing our duplicate form components and maybe standardizing using Formik.