Add kitchen docker tests

.kitchen.docker.yml

@@ -0,0 +1,77 @@
+---
+driver:
+  name: docker
+
+provisioner:
+  name: puppet_apply
+  manifests_path: environments/etc/manifests
+  modules_path: /tmp/modules
+  require_puppet_repo: true
+  require_chef_for_busser: false
+  puppet_debug: true
+  puppet_verbose: true
+  custom_pre_apply_command: 'cp -r /tmp/modules/* /tmp/kitchen/modules/'
+
+platforms:
+  - name: centos-7
+    driver_config:
+      # we use a custom image that runs systemd
+      image: 'datadog/docker-library:chef_kitchen_systemd_centos_7'
+      run_command: /root/start.sh
+
+    driver:
+      provision_command:
+        - rpm -ivh http://yum.puppetlabs.com/puppetlabs-release-el-7.noarch.rpm
+        - yum install -y puppet
+
+        - mkdir /home/kitchen/puppet
+        - printf <%= File.read('environments/etc/Puppetfile').inspect %> > /home/kitchen/puppet/Puppetfile
+
+        - gem install r10k -v 2.6.7
+        - cd /home/kitchen/puppet && r10k puppetfile install --moduledir=/tmp/modules
+
+  - name: centos-8
+    driver_config:
+      # we use a custom image that runs systemd
+      image: 'datadog/docker-library:chef_kitchen_systemd_centos_8'
+      run_command: /root/start.sh
+
+    driver:
+      provision_command:
+        - dnf install -y https://yum.puppetlabs.com/puppet-release-el-8.noarch.rpm
+        - dnf install -y puppet
+
+        - mkdir /home/kitchen/puppet
+        - printf <%= File.read('environments/etc/Puppetfile').inspect %> > /home/kitchen/puppet/Puppetfile
+
+        - gem install r10k -v 2.6.7
+        - cd /home/kitchen/puppet && r10k puppetfile install --moduledir=/tmp/modules
+
+  - name: ubuntu-16.04 # we use the official image
+    driver:
+      provision_command:
+        - apt-get install -y apt-utils apt-transport-https ca-certificates
+        - wget https://apt.puppetlabs.com/puppet6-release-xenial.deb
+        - dpkg -i puppet6-release-xenial.deb
+        - apt-get install -y puppet
+
+        - mkdir /home/kitchen/puppet
+        - printf <%= File.read('environments/etc/Puppetfile').inspect %> > /home/kitchen/puppet/Puppetfile
+
+        - gem install r10k -v 2.6.7
+        - cd /home/kitchen/puppet && r10k puppetfile install --moduledir=/tmp/modules
+
+verifier:
+  name: serverspec
+
+suites:
+  - name: dd-agent
+    manifests: init.pp
+    verifier:
+      default_pattern: true
+      additional_install_commmand: source /etc/profile.d/rvm.sh
+      env_vars:
+        TARGET_HOST: 127.0.0.1
+        TARGET_PORT: 2222
+        LOGIN_USER: root
+        LOGIN_PASSWORD: puppet