Refactor cinder plugin and extend it with multiple backends support

Closes-Bug: rhbz#1139246
Change-Id: I9803939d45e9bafea9b21274a4c64248a037cd33

packstack/puppet/templates/cinder_vmdk.pp

@@ -1,5 +1,11 @@
-class { 'cinder::volume::vmdk':
+cinder::backend::vmdk { 'vmdk':
   host_ip       => "%(CONFIG_VCENTER_HOST)s",
   host_username => "%(CONFIG_VCENTER_USER)s",
   host_password => "%(CONFIG_VCENTER_PASSWORD)s",
 }
+
+cinder::type { 'vmdk':
+  set_key   => 'volume_backend_name',
+  set_value => 'vmdk',
+  require   => Class['cinder::api'],
+}