quota-class-update doesn't work for --fixed_ips

There is a fixed_ips default quota of -1 but novaclient doesn't support updating that field.

Here are defaults:

[root@vs212 ~]# nova quota-defaults
+-----------------------------+-------+
| Quota | Limit |
+-----------------------------+-------+
| instances | 10 |
| cores | 20 |
| ram | 51200 |
| floating_ips | 10 |
| fixed_ips | -1 |
| metadata_items | 128 |
| injected_files | 5 |
| injected_file_content_bytes | 10240 |
| injected_file_path_bytes | 255 |
| key_pairs | 100 |
| security_groups | 10 |
| security_group_rules | 20 |
+-----------------------------+-------+

This fails when trying to update --fixed_ips:

[root@vs212 ~]# nova quota-class-update --fixed_ips 5
usage: nova [--version] [--debug] [--os-cache] [--timings]
            [--timeout <seconds>] [--os-auth-token OS_AUTH_TOKEN]
            [--os-username <auth-user-name>] [--os-password <auth-password>]
            [--os-tenant-name <auth-tenant-name>]
            [--os-tenant-id <auth-tenant-id>] [--os-auth-url <auth-url>]
            [--os-region-name <region-name>] [--os-auth-system <auth-system>]
            [--service-type <service-type>] [--service-name <service-name>]
            [--volume-service-name <volume-service-name>]
            [--endpoint-type <endpoint-type>]
            [--os-compute-api-version <compute-api-ver>]
            [--os-cacert <ca-certificate>] [--insecure]
            [--bypass-url <bypass-url>]
            <subcommand> ...
error: unrecognized arguments: --fixed_ips
Try 'nova help ' for more information.

This is because --fixed_ips isn't a listed var for the shell command:

http://git.openstack.org/cgit/openstack/python-novaclient/tree/novaclient/v1_1/shell.py#n3424