Add option for whether the cloud supports floating ips

This commit adds a new config option to specify whether the cloud under
test supports floating ips or not. Not every cloud supports floating ips
so we need to be able to handle that and properly skip tests.

Change-Id: Iedc3c7f9d045408f54d94c34b478fb1b28b593c9
Closes-Bug: #1603492
17 files changed