[xenserver] added new methods to StorageRepository model

- destroy/save operations
- generic set_attribute method

lib/fog/xenserver/models/compute/storage_repository.rb

@@ -40,6 +40,49 @@ module Fog
           reload
         end
 
+        def destroy
+          connection.destroy_sr reference
+        end
+        
+        def save
+          requires :name
+          requires :type
+
+          # host is not a model attribute (not in XAPI at least), 
+          # but we need it here
+          host = attributes[:host]
+          raise ArgumentError.new('host is required for this operation') unless
+            host
+
+          # Not sure if this is always required, so not raising exception if nil
+          device_config = attributes[:device_config]
+
+          # create_sr request provides sane defaults if some attributes are
+          # missing
+          attr = connection.get_record(
+            connection.create_sr( host.reference, 
+                                  name,
+                                  type,
+                                  description,
+                                  device_config,
+                                  physical_size,
+                                  content_type,
+                                  shared || false,
+                                  sm_config),
+            'SR'
+          )
+          merge_attributes attr 
+          true
+        end
+        
+        def set_attribute(name, *val)
+          data = connection.set_attribute( 'SR', reference, name, *val )
+          # Do not reload automatically for performance reasons
+          # We can set multiple attributes at the same time and
+          # then reload manually
+          #reload
+        end
+
       end
       
     end