Bug Description

When i use "volume qos create" command to create a qos for volume. I find a useless show in the item of specs:
➜ python- openstackclient git:(func- volume- qos) #openstack volume qos create hello
+------ ----+-- ------- ------- ------- ------- ------- -+
| Field | Value |
+------ ----+-- ------- ------- ------- ------- ------- -+
| consumer | both |
| id | 39a23ac7- b5e3-4a0a- 8f03-38aa3cb4b1 e8 |
| name | hello |
| specs | {} |
+------ ----+-- ------- ------- ------- ------- ------- -+
➜ python- openstackclient git:(func- volume- qos) #openstack volume qos create hello1 --consumer front-end --property a=b
+------ ----+-- ------- ------- ------- ------- ------- -+
| Field | Value |
+------ ----+-- ------- ------- ------- ------- ------- -+
| consumer | front-end |
| id | 6190c068- d129-4dc8- b408-54760b6715 d1 |
| name | hello1 |
| specs | {u'a': u'b'} |
+------ ----+-- ------- ------- ------- ------- ------- -+
As is showed above,it will show useless { } in specs, when i set '--property' option.