[aws|compute] add tagSet to describe format

lib/fog/aws/requests/compute/create_volume.rb

@@ -47,6 +47,7 @@ module Fog
               'size'              => size,
               'snapshotId'        => snapshot_id,
               'status'            => 'creating',
+              'tagSet'            => {},
               'volumeId'          => volume_id
             }
             @data[:volumes][volume_id] = data

tests/aws/requests/compute/volume_tests.rb

@@ -27,6 +27,7 @@ Shindo.tests('AWS::Compute | volume requests', ['aws']) do
       'size'              => Integer,
       'snapshotId'        => NilClass,
       'status'            => String,
+      'tagSet'            => {},
       'volumeId'          => String
     }],
     'requestId' => String