Add parameter to volume list request

Change-Id: I9700f2d53ce3c873759946b51f69ca4e056595c1
diff --git a/openstack/blockstorage/v2/volumes/requests.go b/openstack/blockstorage/v2/volumes/requests.go
index 44f6240..a51eebc 100644
--- a/openstack/blockstorage/v2/volumes/requests.go
+++ b/openstack/blockstorage/v2/volumes/requests.go
@@ -91,6 +91,8 @@
 	Name string `q:"name"`
 	// List only volumes that have a status of Status.
 	Status string `q:"status"`
+	// The ID of the last-seen item.
+	Marker string `q:"marker"`
 }
 
 // ToVolumeListQuery formats a ListOpts into a query string.
diff --git a/openstack/blockstorage/v3/volumes/requests.go b/openstack/blockstorage/v3/volumes/requests.go
index 44f6240..a51eebc 100644
--- a/openstack/blockstorage/v3/volumes/requests.go
+++ b/openstack/blockstorage/v3/volumes/requests.go
@@ -91,6 +91,8 @@
 	Name string `q:"name"`
 	// List only volumes that have a status of Status.
 	Status string `q:"status"`
+	// The ID of the last-seen item.
+	Marker string `q:"marker"`
 }
 
 // ToVolumeListQuery formats a ListOpts into a query string.