
Devstack master(Victoria) has dropped xenial distro, switch base box version to bionic. Bionic has puppet5 as default puppet version, which has faster puppet class running in parallel, so devstack and grenade repos were being checked out while /home/stack dir were still being created, impose puppet class ordering. Change-Id: I89af65ca8c53aa41407ed7e4ca0edef88daae3b9