Add '--from-port-id' for port-create

[LiuYong]

For admin, there is a need that clone a port, and i think it is conveniently that port-create command is attached a parameter '--from-port-id'.

Use cases
=========
In certain commercial scenery, such as DC cases using TECS of ZTE, it is always been mentioned that a port should be cloned from a existing port. The succeeder inherit the reasonable properties of the former, such like parent network, mtu, qos-policy and security-group, etc.

Now like below:
============
Now, port-create command of neutron has no similar parameter.

I think it should be:
=====================
[root@localhost devstack]# neutron port-create clone_one --from-port-id 394d5dc8-57e1-4bb6-8e05-9f7965fe57ff
Created a new port inherited from 394d5dc8-57e1-4bb6-8e05-9f7965fe57ff:
+-----------------------+----------------------------------------------------------------------------------+
| Field | Value |
+-----------------------+----------------------------------------------------------------------------------+
| admin_state_up | True |
| allowed_address_pairs | |
| binding:host_id | |
| binding:profile | {} |
| binding:vif_details | {} |
| binding:vif_type | unbound |
| binding:vnic_type | normal |
| created_at | 2016-08-08T18:08:13 |
| description | |
| device_id | |
| device_owner | |
| extra_dhcp_opts | |
| fixed_ips | {"subnet_id": "fd8cb18b-842d-44f4-97c5-2bc110ff36a1", "ip_address": "10.10.0.9"} |
| id | 52a75cf5-8447-48c0-a21a-34acf3baa278 |
| mac_address | fa:16:3e:44:74:ac |
| name | |
| network_id | d9da67c4-42c5-4db5-be3e-51376b310ae7 |
| port_security_enabled | True |
| security_groups | 8acc88a6-f4af-478d-963f-f35d8548e7f0 |
| status | DOWN |
| tenant_id | 48f4bc5cdb8d44a5a41b2e719c1e54ee |
| updated_at | 2016-08-08T18:08:13 |
+-----------------------+----------------------------------------------------------------------------------+

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

Bug closed due to lack of activity, please feel free to reopen if needed.