VA: Use correct Timeout for SimplifiedVAHTTP reqs. (#4046)
VA: Use correct Timeout for SimplifiedVAHTTP reqs. (#4046)

The `DefaultTransport`'s `DialContext` sets a `Timeout` and `KeepAlive`
of 30 seconds. When configured with the `SimplifiedVAHTTP` feature flag
we need to use a shorter `Timeout`.
letsencrypt/boulder,jcjones/boulder,jfrazelle/boulder,bmw/boulder,jsha/boulder,jfrazelle/boulder,jcjones/boulder,letsencrypt/boulder,bmw/boulder,jsha/boulder,jfrazelle/boulder,bmw/boulder,jcjones/boulder,jfrazelle/boulder,jcjones/boulder,letsencrypt/boulder,jsha/boulder