Switch to namespace sdtlib functions

puppetlabs-stdlib deprecated the existing functions in favor of
the new stdlib:: functions in 9.0.0. The version was released a few
years ago and now we assume we are ready to adopt to the migration.

Change-Id: I4cf5919830d3237f25f9b7d719174aa0f93bdfaf
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

manifests/init.pp

@@ -347,7 +347,7 @@ class cloudkitty(
     file {'metrics.yml':
       ensure  => present,
       path    => $::cloudkitty::params::metrics_yaml,
-      content => to_yaml($metrics_config),
+      content => stdlib::to_yaml($metrics_config),
       mode    => '0640',
       owner   => 'root',
       group   => $::cloudkitty::params::group,

metadata.json

@@ -11,7 +11,7 @@
         },
         {
             "name": "puppetlabs/stdlib",
-            "version_requirement": ">=5.0.0 <10.0.0"
+            "version_requirement": ">=9.0.0 <10.0.0"
         },
         {
             "name": "openstack/openstacklib",