Use rancher/os-system-docker to download system-docker

Bump system-docker from 17.06-ros5 to 17.06-ros6

Use rancher/os-system-docker to download system-docker

Remove integration tests

Generate sshd_config by go template

Support instance/attributes/block-project-ssh-keys for gce metadata

Move multiple user-docker images to rancher/os-dind

Update vmware release script

Enhance the clean script

(cherry picked from commit 4907fc9)

Add cloud-config for noformat install-type

(cherry picked from commit 90e88cf)