Improve chef14 support (#30)

* Fix issue with chef 14
* Add chef 14 and ubuntu 18.04 to tests

Author: ivadim

.kitchen.yml

@@ -36,6 +36,12 @@ platforms:
       box: ubuntu/artful64
     provisioner:
       require_chef_omnibus: 13.6.4
+  
+  - name: ubuntu1804
+    driver_config:
+      box: ubuntu/bionic64
+    provisioner:
+      require_chef_omnibus: 14.3.37
 
   - name: centos7
     driver_config:
@@ -97,6 +103,7 @@ suites:
       - debian9
       - ubuntu1604
       - ubuntu1710
+      - ubuntu1804
       - centos7
 
     attributes:

libraries/helpers.rb

@@ -7,7 +7,7 @@ module Helpers
       require 'json'
       require 'fileutils'
 
-      def archive_name(version)
+      def get_archive_name(version)
         name = 'vsts_agent'
         name += '_' + version if version
         name

resources/default.rb

@@ -57,7 +57,7 @@
 
   converge_if_changed do
     archive_url = download_url(version)
-    archive_name = archive_name(version)
+    archive_name = get_archive_name(version)
     unpack_dir = ::File.join(Chef::Config[:file_cache_path], 'unpack_agent')
     unpack_dir = win_friendly_path(unpack_dir) if windows?