Add 'reserved' status to api-ref
@@ -23,6 +23,8 @@ status values are:
+------------------+--------------------------------------------------------+
| available | The volume is ready to attach to an instance. |
+------------------+--------------------------------------------------------+
+| reserved | The volume is reserved for attaching or shelved. |
++------------------+--------------------------------------------------------+
| attaching | The volume is attaching to an instance. |
+------------------+--------------------------------------------------------+
| detaching | The volume is detaching from an instance. |
