Add config option for floating ip support

[Matthew Treinish]

There are certain neutron configurations that do not support using floating ips. For example, when running with ipv6 only. We need a configuration flag for this in tempest to ensure we don't attempt to create a floating ip in these configurations because it will inevitably fail.

An example of this in a run with ipv6 only can be found here:

http://logs.openstack.org/47/210647/2/check/gate-tempest-dsvm-neutron-full/ea565de/console.html

[Matthew Treinish (treinish)]

The likely place for this option will be the network-feature-enabled group. Then we just need to check it before anything that tries to do a floating ip create, and either skip or use a fixed ip if it's set to False depending on the test.

[Andrea Frittoli (andrea-frittoli)]

This is 1y+ old. It seems to be valid still, but there was not action on it. Shuquan Huang, are you still working on it?

[Ken'ichi Ohmichi (oomichi)]

Alternative bug is younger than this, but the bug contains useful discussion.
So I marked this as duplicated.