service validation: log output on failures

When validating a service, it's useful to have logs when exec output
fails.
This patch adds this feature.

Change-Id: I43c9eff8516ea562bf9bde8d5651ddceeb496163

manifests/service_validation.pp

@@ -76,6 +76,7 @@ define openstacklib::service_validation(
     try_sleep => $try_sleep,
     onlyif    => $onlyif,
     unless    => $unless,
+    logoutput => 'on_failure',
   }
 
   anchor { "create ${service_name} anchor":

spec/defines/openstacklib_service_validation_spec.rb

@@ -38,6 +38,7 @@ describe 'openstacklib::service_validation' do
         :command   => 'nova list',
         :tries     => '10',
         :try_sleep => '2',
+        :logoutput => 'on_failure',
       )}
 
       it { is_expected.to contain_anchor("create #{title} anchor").with(