Use puppet() instead of shell() to install module dependencies

spec/spec_helper_acceptance.rb

@@ -28,7 +28,7 @@ RSpec.configure do |c|
     hosts.each do |host|
       copy_module_to(host, :source => proj_root, :module_name => 'apt')
       shell("/bin/touch #{default['puppetpath']}/hiera.yaml")
-      shell('puppet module install puppetlabs-stdlib --version 2.2.1', { :acceptable_exit_codes => [0,1] })
+      on host, puppet('module install puppetlabs-stdlib --version 2.2.1'), { :acceptable_exit_codes => [0,1] }
     end
   end
 end