[openstack|compute] Added get server volumes request

lib/fog/openstack/compute.rb

@@ -130,6 +130,7 @@ module Fog
       request :delete_volume
       request :attach_volume
       request :detach_volume
+      request :get_server_volumes
 
       request :create_volume_snapshot
       request :list_snapshots

lib/fog/openstack/requests/compute/get_server_volumes.rb

@@ -0,0 +1,23 @@
+module Fog
+  module Compute
+    class OpenStack
+      class Real
+
+        def get_server_volumes(server_id)
+
+          request(
+            :expects  => 200,
+            :method   => 'GET',
+            :path     => "/servers/#{server_id}/os-volume_attachments"
+          )
+        end
+
+      end
+
+      class Mock
+
+      end
+
+    end
+  end
+end