[cloudstack] Add get snapshots for volume

lib/fog/cloudstack/models/compute/snapshots.rb

@@ -7,8 +7,9 @@ module Fog
       class Snapshots < Fog::Collection
         model Fog::Compute::Cloudstack::Snapshot
 
-        def all
-          data = service.list_snapshots["listsnapshotsresponse"]["snapshot"] || []
+        def all(attributes = {})
+          response = service.list_snapshots(attributes)
+          data = response["listsnapshotsresponse"]["snapshot"] || []
           load(data)
         end
 

lib/fog/cloudstack/models/compute/volume.rb

@@ -58,6 +58,11 @@ module Fog
           end
         end
 
+        def snapshots
+          requires :id
+          service.snapshots.all('volumeid' => id)
+        end
+
         def reload
           requires :identity