Ensure swift hash is rebuilt for every puppet run

Previously, the swift caches were being built on the class
instances themselves.

This could result in stale values when puppet runs multiple times
using the same process (like in the case of puppet agent)

This commit uses prefetch to ensure that the retrieved swift ring
values are updated per puppet run.

lib/puppet/provider/ring_account_device/swift_ring_builder.rb

@@ -6,6 +6,14 @@ Puppet::Type.type(:ring_account_device).provide(
 
   optional_commands :swift_ring_builder => 'swift-ring-builder'
 
+  def self.prefetch(resource)
+    @my_ring = lookup_ring
+  end
+
+  def self.ring
+    @my_ring ||= lookup_ring
+  end
+
   # TODO maybe this should be a parameter eventually so that
   # it can be configurable
   def self.builder_file_path

lib/puppet/provider/ring_container_device/swift_ring_builder.rb

@@ -6,6 +6,14 @@ Puppet::Type.type(:ring_container_device).provide(
 
   optional_commands :swift_ring_builder => 'swift-ring-builder'
 
+  def self.prefetch(resource)
+    @my_ring = lookup_ring
+  end
+
+  def self.ring
+    @my_ring ||= lookup_ring
+  end
+
   # TODO maybe this should be a parameter eventually so that
   # it can be configurable
   def self.builder_file_path

lib/puppet/provider/ring_object_device/swift_ring_builder.rb

@@ -6,6 +6,14 @@ Puppet::Type.type(:ring_object_device).provide(
 
   optional_commands :swift_ring_builder => 'swift-ring-builder'
 
+  def self.prefetch(resource)
+    @my_ring = lookup_ring
+  end
+
+  def self.ring
+    @my_ring ||= lookup_ring
+  end
+
   # TODO maybe this should be a parameter eventually so that
   # it can be configurable
   def self.builder_file_path

lib/puppet/provider/swift_ring_builder.rb

@@ -8,9 +8,6 @@ class Puppet::Provider::SwiftRingBuilder < Puppet::Provider
     end
   end
 
-  def self.ring
-    @my_ring ||= lookup_ring
-  end
 
   def self.lookup_ring
     object_hash = {}