Support Raspbian as debian-based systems (DataDog#719)

Author: Mstrodl

manifests/init.pp

@@ -425,7 +425,7 @@
   # Install agent
   if $manage_install {
     case $::operatingsystem {
-      'Ubuntu','Debian' : {
+      'Ubuntu','Debian','Raspbian' : {
         if $use_apt_backup_keyserver != undef or $apt_backup_keyserver != undef or $apt_keyserver != undef {
           notify { 'apt keyserver arguments deprecation':
             message  => '$use_apt_backup_keyserver, $apt_backup_keyserver and $apt_keyserver are deprecated since version 3.13.0',

manifests/params.pp

@@ -24,7 +24,7 @@
   $module_metadata                = load_module_metadata($module_name)
 
   case $::operatingsystem {
-    'Ubuntu','Debian' : {
+    'Ubuntu','Debian','Raspbian' : {
       $rubydev_package            = 'ruby-dev'
       $legacy_conf_dir            = '/etc/dd-agent/conf.d'
       $conf_dir                   = '/etc/datadog-agent/conf.d'