Allow reassociate for associated FIPs

[Brad Pokorny]

The Compute -> Access & Security -> Floating IPs tab should provide the Associate button for FIPs that are already associated. The nova CLI allows a user to associate an already associated FIP, with the behavior being that the FIP is transferred from one VM to another.

$ openstack --debug ip floating add [Already associated IP] [VM to reassign the FIP to]
....
REQ: curl -g -i -X POST https://nova-api.example.com/v2/[project ID]/servers/[Instance ID]/action -H "User-Agent: python-novaclient" -H "Content-Type: application/json" -H "Accept: application/json" -H "X-Auth-Token: {SHA1} [token hash]" -d '{"addFloatingIp": {"address": "[IP address]"}}'
"POST /v2/[project ID]/servers/[Instance ID]/action HTTP/1.1" 202 0
....

The single API call to nova associates the IP with the new VM and disassociates it from the old VM. The CLI behavior is especially useful for service IP's, where switching an IP from one VM to another quickly is important.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Rob Cresswell (<email address hidden>) on branch: master
Review: https://review.openstack.org/283223
Reason: Abandoned due to inactivity. Feel free to restore if you get time to work on it

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/534966

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/535163

[OpenStack Infra (hudson-openstack)]

Change abandoned by Emma Hogan (<email address hidden>) on branch: master
Review: https://review.openstack.org/535163

[OpenStack Infra (hudson-openstack)]

Change abandoned by Akihiro Motoki (<email address hidden>) on branch: master
Review: https://review.openstack.org/534966
Reason: The original patch was restored. This is no longer needed.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Ivan Kolodyazhny (<email address hidden>) on branch: master
Review: https://review.openstack.org/283223
Reason: This review is > 4 months without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.