Added the macOS 10.15 Catalina builder to the dashboard. Catalina builders should
use the Mojave guestid in vSphere 6.7 update 3 because the Catalina guestid is not
available in this version of vSphere. A Catalina builder will run on this version
of vSphere with the Mojave guestid. Modified the expected number of vm instances
running on Macstadium due to the addition of macOS 10.15 builders.
Reviewed-by: Brad Fitzpatrick <firstname.lastname@example.org>
Reviewed-by: Dmitri Shuralyov <email@example.com>