voxupuli-acceptance: Update 4.1->4.2

4.2 brings and updated `curl_command` which allows us to configure
client TLS certificates and username/password. We want to use that in
puppet-foreman:

theforeman/puppet-foreman#1251

Author: bastelfreak

config_defaults.yml

@@ -28,7 +28,7 @@ Gemfile:
       groups:
       - 'development'
   - gem: 'voxpupuli-acceptance'
-    version: '~> 4.1'
+    version: '~> 4.2'
     options:
       groups:
         - 'system_tests'