dashboard: rebuild FreeBSD VM to avoid 10 second boot prompt
dashboard: rebuild FreeBSD VM to avoid 10 second boot prompt

FreeBSD VMs boot up 10 seconds faster now, and shut down faster.

Updates golang/go#22894
Updates golang/go#22895

Change-Id: I8eef979fc43d95d3c03104a761e70ec5737a3a97
Reviewed-on: https://go-review.googlesource.com/80304
Reviewed-by: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>

golang/build,golang/build,golang/build,golang/build