Merge pull request #2317 from kubernetes-incubator/add_digitalocean_ci

.gitlab-ci.yml

Dockerfile

tests/Makefile

tests/cloud_playbooks/create-do.yml

tests/files/do_ubuntu-canal-ha.yml

tests/files/gce_centos-weave-kubeadm.yml

tests/files/gce_centos7-calico-ha.yml

tests/files/gce_centos7-flannel-addons.yml

tests/files/gce_coreos-alpha-weave-ha.yml

tests/files/gce_coreos-calico-aio.yml

tests/files/gce_coreos-canal.yml

tests/files/gce_debian8-calico-upgrade.yml

tests/files/gce_rhel7-canal-sep.yml

tests/files/gce_rhel7-weave.yml

tests/files/gce_ubuntu-canal-ha.yml

tests/files/gce_ubuntu-canal-kubeadm.yml

tests/files/gce_ubuntu-contiv-sep.yml

tests/files/gce_ubuntu-flannel-sep.yml

tests/files/gce_ubuntu-rkt-sep.yml

tests/files/gce_ubuntu-vault-sep.yml