Chef 17 compatibility changes

Author: bmhughes

kitchen.dokken.yml

@@ -2,6 +2,7 @@
 driver:
   name: dokken
   privileged: true
+  chef_version: <%= ENV['CHEF_VERSION'] || 'latest' %>
 
 transport:
   name: dokken

resources/_user_ssh.rb

@@ -16,6 +16,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+unified_mode true
+
 include UserSsh::Cookbook::GeneralHelpers
 
 property :cookbook, String,